Biological and psychological research into the antecedents of altruism has considerable significance for those involved in the teaching or practice of medicine. The evidence available indicates that altruistic behaviour is a universal phenomenon influenced by intra-individual, interpersonal, situational and sociocultural factors. A central theme which emerges is the strikingly ambivalent nature of the altruistic drive. The factors which may facilitate or inhibit altruism in medical students and doctors are discussed. Some ways of ensuring that medical training does not seriously distort altruism are suggested.