a physician of Iulus, a town of the island of Ceos, now Zea, off Cape Sunium, in Attica, flourished from about 300 to 258 B.C. According to one account, he was grandson of Aristotle, his mother being daughter of that philosopher. He seems to have been in high favour at the court of Seleucus Nicator, whose son Antiochus he recovered from a dangerous illness in the following manner: Antiochus was violently enamoured of his mother-in-law Stratonice, and he determined to rid himself of life. His physician, Erasistratus, by close observation, perceived that Stratonice was the cause of his illness; and having informed his father, that monarch allowed his son to marry her. A similar story is told of many ancient physicians.

In his old age he renounced the practice of medicine, and, retiring to Alexandria, devoted himself more particularly to the study of anatomy. His description of the brain and nerves is said to have been far more correct than that of any of his predecessors. He was the founder of a school of medicine, which flourished long at Smyrna, and the disciples of which continued to exist till the time of Galen. Of his works only a few fragments remain, in the quotations of Galen and other writers.