Secondary amenorrhea in athletes is reviewed with respect to its incidence, treatment, associated characteristics, proposed mechanisms, and endocrine profile. Athletic amenorrhea is classified within the general category of chronic anovulation syndrome, but no mechanism has been demonstrated. The wide range in observed incidences (1-44%) is due to the lack of a standard definition for secondary amenorrhea and differences between the populations surveyed. The currently recommended treatment is outlined briefly. Several descriptive characteristics of amenorrheic athletes have led to a variety of proposed mechanisms involving body composition, training regimen, reproductive maturity, sport specificity, diet, and psychological stress. Basal hormone concentrations in eumenorrheic women after training and in amenorrheic athletes, as well as transitory endocrine responses to exercise, are the basis for evaluating these proposals. Methodological errors which have led to conflicting results are identified, and the proposed mechanisms are evaluated on the basis of the presently available data.