Twenty male marathon athletes were evaluated by hormonal profiles, psychologic testing, anthropomorphic indices, and semen evaluations. Although total testosterone (T) was significantly decreased in 14 of 20 subjects, free testosterone (FT) was within the normal range in the majority. Ninety percent of subjects (18 of 20) had normal semen analyses. Running mileage, body fat, T, and FT values did not correlate with semen quality. Two athletes with severe oligospermia were found to have the lowest values of T and FT and significant differences in psychologic stress scores. From these data we conclude that (1) vigorous endurance training may be associated with significantly decreased T values but not sperm production; (2) a subgroup of severely oligospermic athletes may be characterized by an "anorectic" symptom complex including higher stress, increased body leanness, and significantly decreased T levels; (3) male endocrine evaluation should be interpreted within the context of physical activity; and (4) factors other than T levels need to be evaluated when one is formulating a therapy plan in oligospermic male athletes.