Premature androgenetic alopecia has been suggested as a sign of the male equivalent of polycystic ovary syndrome. However, the hormonal background of men with premature baldness has been studied in only a few studies with conflicting results. We examined 37 men with premature alopecia (defined as frontal-parietal and parietal alopecia under the age of 30 years with alopecia defined as grade 3 or more apical alopecia on the Hamilton alopecia classification scale with the Norwood modification). Plasma concentrations of total testosterone, dihydrotestosterone, epitestosterone, androstenedione, cortisol, 17-OH-progesterone (17OHP), estradiol, LH, FSH, prolactin, SHBG and TSH, and free thyroxine were measured. The frequency of subnormal values of SHBG, FSH, testosterone, and epitestosterone (but not in the free androgen index) was significant in balding men. A borderline significant trend was observed for elevated levels of 17OH-P and prolactin. The hormonal background of a significant number of men with premature baldness in some respects resembles the hormonal background of women with polycystic ovary syndrome.