More than half the species in Sapindales belong to two families: Sapindaceae (about 1,600 species) and Rutaceae (about 1,800 species). Most of the remaining species belong to four other well-known families: Anacardiaceae (about 600 species), Burseraceae (550 species), Meliaceae (621 species), and Simaroubaceae (95 species). The remaining three families (Biebersteiniaceae, Kirkiaceae, and Nitrariaceae) total 27 species.

Sapindales is placed in the Rosid II group, along with Huerteales, Malvales, and Brassicales, in the Angiosperm Phylogeny Group II botanical classification system (see angiosperm).

Included within Sapindaceae are the genera from two former families, Aceraceae and Hippocastanaceae. The most important genus in Aceraceae was Acer ( maple), with about 110 species, which is found across the north temperate zone from western North America to Japan. Maple trees form an important component of the deciduous forests of North America, Europe, and Asia. The distribution of the genus dips southward to Guatemala and through Southeast Asia to Malaysia and the Philippines, where species may be abundant in tropical mountain forests. The major centre of distribution for the genus is China, where half the maple species occur; about three-quarters of the species are Asian. There are eight species of Acer with compound leaves that are sometimes placed in a separate genus, Negundo. Another former member of Aceraceae is Dipteronia, a genus of central and southern China with two species.

Useful oils are expressed from the seeds of wild prune and Schleichera oleosa (Ceylon oak); the latter is the source of macassar oil, and this species harbours Laccifer lacca, the insect that produces lac, a resinous excretion that is a source of shellac.

The seeds of the Brazilian and Paraguayan vine Paullinia cupana ( guarana) are ground to make a beverage that contains three times as much caffeine as found in a cup of coffee; a stimulating tea used in pre-Columbian South America, guarana became a popular ingredient in energy drinks beginning in the 20th century. The bark of Paullinia yoco (yoco) has similar stimulant properties.

The best-known member of the previously recognized family Aceraceae is Acer saccharum ( sugar maple). It has sugar-rich sap that is tapped in the early spring in eastern North America in order to make maple syrup and maple sugar. Sugar maple has been described as the most valuable hardwood in North America. Its figured wood (curly maple and bird's-eye maple) is valued for cabinetry and furniture; the plain wood is used for construction, flooring, and interior finish. The hard, strong, heavy close-grained wood is often beautifully patterned. The sugar maple is a valuable ornamental and shade tree because of its thick shapely crown and the bright yellow, orange, and red autumnal coloration. In addition, it yields valuable firewood. Other North American maple species are less important as timber, paper pulp, sugar-producing, and ornamental trees. A few European species, and more Asian species, are sources of timber or grown as ornamentals for their foliage and leaf colours.

The six or seven species of Khaya in tropical Africa and Madagascar, including K. senegalensis (African mahogany), produce a wood like that of mahogany, as do the nine species of omu, sapele, and utile mahoganies (Entandrophragma). Important Asian timber trees are Toona ciliata (Australian red cedar, or Indian mahogany; grown throughout South Asia, New Guinea, and Australia), Chukrasia tabularis (Chittagong wood; grown in China and Indo-Malaysia), and Soymida febrifuga (Indian redwood; grown in Indo-Malaysia). Dysoxylum fraserianum (Australian mahogany) is a timber tree of the forests of northern and eastern Australia. The wood of these genera, all of Meliaceae, is typically reddish in colour, lustrous, easy to work, and free of warping under changes in relative humidity. Such characteristics make the wood highly suited for cabinetmaking.

Some species of Meliaceae have medicinal properties. The bark of the Indo-Malaysian Azadirachta indica (neem) is astringent and may also be used to make an insecticide. The bark of Guarea rusbyi (cocillana) from South America is an emetic. The seeds of other species yield useful oils. Several species of Carapa produce oils used for soap: in South America C. guianensis (crabwood), in Indo-Malaysia C. procera, and in East Africa Trichilia emetica (cape mahogany). The seeds of the Malayan Chisocheton macrophyllus are a source of an oil used for burning in lamps.

A few members of Meliaceae have edible fruits. Popular in Southeast Asia are Lansium domesticum (langsat) and Sandoricum koetjape (santol), while the flowers of Aglaia odorata are used in East Asia to flavour tea. Melia azedarach (chinaberry, or China tree), a Himalayan tree, is widely grown as an ornamental and is particularly common in the southeastern United States. It has clusters of fragrant lilac-coloured flowers and attractive but poisonous yellow berries.

The fruits of Aegle are used medicinally, as are those of Poncirus trifoliata (Chinese hardy orange). Many species of Rutaceae have bitter bark that is medicinal, including the tropical American Angostura febrifuga (angostura) and Galipea officinalis (casparia). The bark of several North American species of Zanthoxylum is chewed for toothache relief.

Only a few species of Rutaceae are important timber trees. The Indo-Malaysian Chloroxylon swietenia ( satinwood), eastern Australian Flindersia oxleyana (Australian yellowwood), and Caribbean Zanthoxylum flavum (West Indian silkwood) are used for veneering and cabinetmaking.

Few Anacardiaceae species have had their wood exploited for building or for cabinetmaking; however, many of them have valuable tannins (tannin) that have been extracted for tanning leather. Schinopsis quebracho-colorado (quebracho) is a major source of tannins in South America, as is Rhus coriaria (Sicilian sumac) in southern Europe. Species of Cotinus, Pistacia, Rhus, and Schinopsis are important sources of tannins for the leather industry.

Exudates from the stems of various species of Anacardiaceae yield lacquers, resins, or gums. The art of lacquering began in China centuries ago, reaching its climax of development during the Ming dynasty (1368–1644 CE). The lacquers used were obtained from Toxicodendron verniciflua ( varnish tree). The milky exudate from this tree darkens and thickens rapidly on exposure to air. Lacquer, when applied as a varnish, provides remarkable protection, as it is unchanged by acids, alkalis, alcohol, or heat up to 70 °C (158 °F). Gluta usitata (Burmese lacquer tree) produces a more slowly drying lacquer. Pistacia lentiscus (mastic tree), from the Mediterranean region, produces mastic, a varnish used for coating metals and oil and watercolour pictures. It is one of the most expensive resins to produce. The tropical American Anacardium humile, A. occidentale, and A. nanum produce cashew gum, a substitute for gum arabic. Not only are they good adhesives, but they also contain a small amount of cashew oil, which can be used as an insect repellent or as a lubricant in the electrical insulation of airplanes.

Like some of the members of Anacardiaceae, most of the members of Burseraceae are known for their aromatic resins or gums. The most famous of these are Boswellia carteri and related species, the sources of frankincense, and Commiphora abyssinica and related species that yield myrrh. C. opobalsamum furnishes balm of Gilead. All grow naturally or are cultivated in arid areas, from Ethiopia to India, with other species that produce resins. They are also used in incense and perfumes. Resin collecting is an important part of the economy in Ethiopia and Somalia. In tropical America, Protium copal ( copal) and other members of Protium are tapped for their resins, which have been used in Central America as incense for religious purposes since pre-Columbian times. Likewise, Bursera simaruba (gumbo-limbo, or incense tree) and other members of Bursera are exploited for turpentine or elemi (an oily resin) in tropical America. Some contain such large amounts of resin and burn so fiercely that they are known as torchwoods (torchwood). Canarium strictum (Indian black dammar tree) and C. commune (Java almond) of Indo-Malaysia, a source of Manila elemi, also produce commercially valuable resins. The seed of the latter, which is cultivated in Australia, is edible, as are those of several other East Asian species, which also may be processed to produce cooking oil. The fruits of C. albumare are eaten like olives.

A few Burseraceae species are important timber trees. Probably the most important of these is Aucoumea klaineana (gaboon mahogany), from West Africa, used for veneers (veneer) and plywood (wood).

Sapindales is overwhelmingly composed of woody plants—mostly trees, large shrubs, and woody climbers. The latter are particularly common in Sapindaceae (Paullinia, Serjania, and Urvillea) and Anacardiaceae (Toxicodendron). Many beautiful forest trees (tree) belong to this order. The largest trees are in Sapindaceae; they include Schleichera oleosa (Ceylon oak), which grows to 60 metres (almost 200 feet) in Myanmar (Burma), Pometia pinnata, which grows to 50 metres (about 165 feet) in New Guinea, and Tristiropsis canarioides, which grows to 45 metres (150 feet) in New Guinea. Several species of Anacardiaceae, such as the Old World tropical Campnosperma auriculata, Mangifera lagenifera, and Buchanania lucida, may reach heights of 33 metres (108 feet). In North America the sugar maple may grow to 35 metres (115 feet) high.

Most species of Sapindales have pinnately compound leaves (with the leaflets of each compound leaf arranged along both sides of a central axis). They are rarely palmately compound (the leaflets radiating from the petiole apex) or simple. Leaves are generally alternately arranged along a stem and are only rarely opposite or whorled. An interesting form of leaf is found in Citrus, where the simple blade is separated from the petiole by a joint. Because this type of leaf occurs in other genera of Rutaceae with compound leaves, it is believed that this is reduced from a compound form. Reduction goes still further in Citrus, in which the first one or two leaves of an axillary bud (a bud located in an axil, or upper angle, between a stem and a branch or leaf) are reduced to spines. Leaves of the Asian genus Chisocheton (family Meliaceae) show indeterminate or continuous growth. Stipules are usually absent from the leaves of members of Sapindales.

The flowers (flower) may be single in the axils of the leaves, or they may be arranged in racemes (spikelike clusters that bloom from the base upward), cymose spikes (clusters blooming from the top downward), or panicles (many-branched clusters). Flowers of most Sapindales appear to be pollinated (pollination) by insects. The coloured petals and sometimes stamens of many of these flowers make them conspicuous; fragrance makes others attractive to insects. The disk at the base of the pistil often secretes an abundance of nectar attractive to insects as well. In some species, cross-pollination is favoured by protandry (maturation of the stamens before the stigma of the same flower is receptive to pollen) or protogyny (the stigma matures first).

In a number of families and genera throughout the order, there is a strong tendency toward obligate cross-pollination through the progressive development away from the typical floral bisexuality (hermaphroditism), in which both sexes are present and functional in the same flower. This culminates in dioecism, a condition where male and female flowers in the species are borne on separate plants. Dioecism has evolved independently in most families. Many members of the order have bisexual and unisexual flowers on the same plant (polygamous). In some inflorescences, for example, the terminal flower is bisexual, while the others are all male or female. This combines the advantages of maximum fertility through inbreeding with increased variability through outcrossing. Many structurally bisexual flowers, as in many maples for example, are functionally unisexual, as either the stamens do not produce fertile pollen, the stigmas are not receptive, or the pistils do not contain ovules. Some species (e.g., Acer platanoides, Norway maple; A. saccharinum, silver maple; and A. spicatum, mountain maple) are self-sterile and must be outcrossed. Most unisexual flowers in the order have become that way after either the pistil or the stamens fail to mature, as the flowers often retain the rudimentary remains of the nonfunctional organ. Thus, although many species of Sapindales have insured cross-pollination and outbreeding, most have not achieved complete anatomical dioecism.

Stamens are usually double in number of petals, with an outer whorl opposite the sepals and an inner whorl opposite the petals. In some species they are equal to the number of petals and alternate with them, while in others there may be three whorls of stamens or a larger number with whorls that are difficult to distinguish. Filaments are usually free, but they may be fused into a tube in most members of Meliaceae and some members of Rutaceae. Anthers have two locules and open lengthwise. In species with unisexual flowers, staminodes (sterile stamens) are usually present in female flowers. There is almost always a nectar-producing disk between the stamens and the pistil.

The pistil is usually compound, but in a few groups (e.g., Zanthoxylum, Rutaceae) there are separate simple pistils in the flower. The ovary is almost always superior and is composed of 1 to 20 carpels. The ovary is usually multilocular, but it may be multilocular at the base and unilocular above in several members of Meliaceae. It is unilocular in simple pistils. Ovules are typically two per locule, although they may be one or several. Styles are usually united and the same number as the carpels. Functionally male flowers often contain a pistillode (sterile pistil).

The fruit in Sapindales is basically a capsule that splits open between the internal partitions, although it has been modified into a number of other types in most families. For example, in Rutaceae one finds capsules (e.g., Ruta, rue), follicles (Zanthoxylum, prickly ash), drupes (Amyris, torchwood), berries (Triphasia, limeberry), samaras ( hop tree), and schizocarps (Helietta, barreta). The fruit of Citrus is a modified berry with a thick rind called a hesperidium, after the golden apples of the Hesperides. In the myth of the Greek hero Heracles, one of Heracles' 12 labours was the fetching of the golden apples kept by the Hesperides. These mythical apples may well have been based upon oranges, which were not grown in the West in ancient times but which the Greeks may have been aware of because of their trade with the East.

When mature, the seeds of Sapindales may be with or without endosperm, the starchy nutrient tissue that supplies energy for the developing embryo. There are commonly one or two seeds per locule. Some genera of Rutaceae (e.g., Citrus and Zanthoxylum) and Anacardiaceae (Mangifera) contain many embryos in a single seed; these embryos may come from different parts of the ovule besides the fertilized egg. (The formation of an embryo from tissue other than the fertilized egg is called apomixis.) The seeds of Meliaceae are often winged and dispersed by wind. In many Sapindaceae and Burseraceae, the seed is surrounded by a colourful fleshy aril that is attractive to birds, which disperse these seeds. Most families have fleshy fruits attractive to mammals and birds and hard seeds that will pass through their alimentary canals (alimentary canal) without harm.

The evolutionary relationships between the families placed in Sapindales, and between them and other orders, are becoming clarified on the basis of DNA sequence data, morphological resemblances, and chemistry. Sapindales is most closely related to Malvales, Brassicales, and Huertales. Sapindales consists of basically three groups of related families. One group includes the families Rutaceae, Meliaceae, and Simaroubaceae, which share a nectary disk between the anthers and carpels and similar secondary compounds. The second group consists of Anacardiaceae, Burseraceae, and Kirkiaceae, which share small flowers. The third group includes Sapindaceae. Previously recognized families of Aceraceae (maples) and Hippocastanaceae (horse chestnuts) have been shown to be closely related temperate offshoots from within the largely tropical Sapindaceae. In addition, there are two ungrouped families: Biebersteiniaceae and Nitrariaceae.