Background: Despite considerable racial and geographical differences in human phenotypes and in the incidence of diseases that may be associated with sex steroid action, there are few data concerning variation in sex steroid levels among populations. We designed an international study to determine the degree to which geography and race influence sex steroid levels in older men. Methods: Using mass spectrometry, concentrations of serum androgens, estrogens, and sex steroid precursors/metabolites were measured in 5003 older men from five countries. SHBG levels were assessed using radioimmunoassay. Results: There was substantial geographical variation in the levels of sex steroids, precursors, and metabolites, as well as SHBG. For instance, Asian men in Hong Kong and Japan, but not in the United States, had levels of total testosterone approximately 20% higher than in other groups. Even greater variation was present in levels of estradiol, SHBG, and dihydrotestosterone. Group differences in body mass index did not explain most geographical differences. In addition, body mass index-independent racial differences were present; Black men had higher levels of estrogens (estradiol, estrone), and Asian men had lower levels of glucuronidated androgen metabolites. Conclusions: On a global scale, there are important geographical and racial differences in the concentrations of serum sex steroids and SHBG in older men.