Little data exist on the effects of adjunctive therapy with leuprolide acetate (LA) in the luteal phase of women with polycystic ovary syndrome (PCOS) undergoing ovulation induction with human menopausal gonadotropin (hMG). Additionally, it is not known whether gonadal steroid concentrations in the luteal phase of induced cycles in PCOS are predictive of pregnancy. In this prospective, randomized study comparing cycles using hMG alone (n = 26) with cycles using hMG with LA (n = 33), no differences were noted between treatment groups in progesterone (P), estradiol (E2), and P:E2 ratios on luteal days 3, 6, and 9. When all treatment cycles were pooled, there were no differences in P, E2, or P:E2 ratios, comparing conception and nonconception cycles. We conclude that adjunctive therapy with LA in PCOS patients undergoing ovulation induction with hMG does not alter the luteal phase concentrations of P, E2, and P:E2. Furthermore, no correlation was found between the serum concentrations of these luteal phase steroids and cycle fecundity.