A. Cornelius Celsus was author, probably during the reign of the Roman Emperor Tiberius (AD 14–37), of a general encyclopedia of agriculture, medicine, military arts, rhetoric, philosophy, and jurisprudence, in that order of subjects. Of all this great work there survives only the eight books on medicine (De Medicina).

In Book I, after an excellent survey of Greek schools (Dogmatic, Methodic, Empiric) of medicine come sensible dietetics that will always be applicable. Book II deals with prognosis, diagnosis of symptoms (which he stresses strongly), and general therapeutics. Book III addresses internal ailments, fevers, and general diseases. Book IV treats local bodily diseases. Next come two pharmacological books, Book V on treatment by drugs of general diseases, and Book VI on local diseases. Books VII and VIII deal with surgery; these books contain accounts of many operations, including amputation.

Celsus was not a professional doctor of medicine or a surgeon, but a practical layman whose On Medicine, written in a clear and neat style for lay readers, is partly a result of his medical treatment of his household (slaves included), and partly a presentation of information gained from many Greek authorities. From no other source can we learn so much of the condition of medical science up to his own time.

The Loeb Classical Library edition of Celsus is in three volumes.