As bishop of Nicastro, Kingdom of Naples, he participated in the Council of Trent in 1562. In 1566 he was a papal ambassador at Venice. He was later employed in the Roman Inquisition (to combat Protestantism) by Pope Gregory XIII, who appointed him patriarch of Jerusalem (1576) and later made him a cardinal (1583). He assumed practically all administration under the ailing pope Gregory XIV, whom he was chosen to succeed as pope as a short-term replacement acceptable to all. In fact,he died two months later.