agency of the United States government that conducts and supports biomedical research into the causes, cure, and prevention of disease. The NIH is an agency of the Public Health Service of the U.S. Department of Health and Human Services. It is the largest single supporter of biomedical research in the country and also provides training for health researchers and disseminates medical information.

The NIH comprises 25 specialized institutes that conduct or support research in various fields of health and disease, including the National Cancer Institute, National Heart, Lung, and Blood Institute, National Institute of Diabetes and Digestive and Kidney Diseases, National Institute of Allergy and Infectious Diseases, National Institute of Child Health and Human Development, National Institute of Dental and Craniofacial Research, National Institute of Environmental Health Sciences, National Institute of General Medical Sciences, National Institute of Neurological Disorders and Stroke, National Eye Institute, National Institute on Aging, and National Institute of Arthritis and Musculoskeletal and Skin Diseases.

In addition to its various institutes, the NIH maintains the National Library of Medicine, which is the foremost source of medical information in the United States. The NIH also maintains several general research centres and the Division of Computer Research and Technology, which uses computer technologies to support health research programs nationwide.

Most of the research funded by the NIH is conducted in medical schools, universities, and other nonfederal institutions. The primary form of funding is the research grant.