Prostate-specific antigen (PSA) is present at very low concentrations in female serum, but it can now be measured with highly sensitive immunoassays. We have found that in female tissues the PSA gene is regulated by steroid hormones through the action of steroid hormone receptors. Thus, we examined whether female serum PSA is associated with hyperandrogenic states. Serum PSA levels were compared between 22 hirsute women with a Ferriman-Gallwey score higher than 8 and 50 women without hirsutism. The results show that PSA levels were higher in hirsute women in comparison with controls. In hirsute women, levels of PSA and 3 alpha-androstanediol glucuronide (3 alpha-AG), a specific metabolite of androgen action, showed a significant positive correlation, whereas PSA and 3 alpha-AG showed a significant negative correlation with patient age. Receiver operating characteristic (ROC) analysis revealed that 3 alpha-AG was a slightly better marker of androgen excess than PSA. We conclude that female serum PSA may be a new biochemical marker of androgen action in females.