Objective: To elucidate the location of leptin and receptors of ovary specimens obtained from patients undergoing hysterectomy by immunohistochemical staining and to determine the effect of leptin on the steroidogenesis of cultured granulosa cells. Method: In the culturing process of the granulosa cells, FSH (1 IU/ml)and leptin (50 ng/ml), IGF-I (50 ng/ml) was administered to each study group (Group I: FSH; Group II: FSH, leptin; Group III: FSH, IGF-I; Group IV: FSH, IGF-I, leptin), and the levels of estradiol, progesterone, androstenedione in the culture media was measured by radioimmunoassay. Statistical analysis was conducted by one-way ANOVA with Scheffe test. Results: The results showed that leptin and leptin receptors were both found to be strongly stained in granulosa and theca cells, and also in some interstitial cells. Leptin receptors were also observed in cultured granulosa cells. While there was no statistically significant difference in the androstnedione concentrations between the groups, estradiol concentrations was significantly decreased in Group IV ($2202.0{pm}151.14$ pg/ml) compared to Group III ($2859.0{pm}122.6$ pg/ml), and progesterone concentrations were also significantly decreased in Group II($4696.3{pm}190.6$ ng/ml) and Group IV ($4517{pm}206.78$ ng/ml) compared to Group III($5546.0{pm}179.5$ ng/ml). Conclustion: The study result of this study suggest that leptin is directly involved in the regulation of ovarian functions, in particular steroidogenesis.