Averroes inherited a long tradition about theriac. He examined its nature, quality and utilization as an antidote of poisons or venoms and as a treatment of diseases. He stated that if the electuary, as antidote, was beneficial to the patient and to the physician, it might be dangerous as a regular and repeated medication of disease since it could transform the human nature and render it poison-like. Averroes's purpose was to analyze the advantages and drawback of theriac. He aimed at inducing physicians to more caution. He conducted a medico-philosophical and ethical reflexion on the validity of the medication and he advised against its prophylactic use.