Aim: To evaluate the serum leptin levels and the effects of flutamide treatment on the leptin levels in women with polycystic ovary syndrome (PCOS). Methods: 20 women with PCOS and 20 controls were enrolled in the study. Leptin levels and leptin response to an oral glucose tolerance test were assessed in both groups before and after a 4-week flutamide therapy period. Results: The leptin levels were similar in both groups at baseline. In the PCOS group, leptin levels and area under curve for leptin levels increased significantly after flutamide treatment. Conclusions: Women with PCOS had similar leptin levels to those of controls with similar age and body mass index. Flutamide treatment led to increased leptin levels and leptin responses to oral glucose tolerance tests in PCOS patients. Further studies are needed to gain insights into the clinical consequences of these effects of flutamide.