 During the follicular phase of the normal menstrual cycle, luteinizing hormone LH pulse frequency decreases during sleep. These decreases may be important to support follicle stimulating hormone FSH synthesis and secretion. Polycystic ovary syndrome PCOS is associated with a persistently rapid gonadotropin hormone-releasing hormone GnRH pulse frequency, an abnormality that may account for many of the hormonal manifestations of PCOS. Although one prior study suggests that nocturnal LH frequency decreases slightly in PCOS, methodological issues limit interpretation. Our preliminary data suggest that nocturnal LH frequency does not decrease in untreated PCOS, but that nocturnal decreases of LH frequency are restored with androgen receptor blockade flutamide in women with PCOS. We have two hypotheses: 1 Prior to flutamide administration, sleep-associated slowing of LH pulse frequency is less pronounced in women with PCOS compared to that of normally-cycling women in the late follicular phase of the menstrual cycle; 2 After 4 weeks of flutamide administration, sleep-associated LH frequency reduction in women with PCOS is similar to that of normally-cycling women in the late follicular phase of the menstrual cycle. Women with PCOS and normally-cycling women will be studied. For each study participant, LH pulse frequency will be determined from 1500 to 0700 h after 4 weeks of flutamide and after 4 weeks of placebo. Flutamide and placebo will be given in random order i.e., cross-over study. Sleep will be formally evaluated. Flutamide will then be given for 4 weeks prior to reassessment of LH pulse frequency. LH pulse frequency will be analyzed by way of hierarchical mixed effect models. We will use statistical analyses to determine: a whether the wake vs. sleep difference in LH frequency is the same for PCOS and normal controls prior to flutamide, and b whether the mean wake vs. sleep difference in LH frequency is the same for the two groups after flutamide. 