Leydig cell tumor of the ovary is a very rare tumor which usually occurs in the postmenopausal age, and which is frequently associated with virilization. It has been classified as a lipid cell tumor due to the presence of intracytoplasmic lipids. However, since up to 25% of these tumors contain little or no lipid, the new term "steroid cell tumor" is proposed for this type of neoplasm. We report a case of Leydig cell tumor of the ovary in a 16 year old girl. The patient exhibited recently recognized hirsuitism and secondary amenorrhea. Physical examination revealed moderate obesity with moderate amounts of coarse hair over the whole body and a deepening of the voice. Testosterone and dehydroepiandrosterone sulfate levels were markedly elevated in the peripheral blood. Pelvic ultrasonography revealed a right ovarian tumor. The resected ovary showed a well demarcated, golden yellow to orange colored solid mass, measuring 7 cm on the cut surface. Microscopically, the tumor was composed of solid and diffuse sheets of tumor cells having abundant eosinophilic cytoplasm, and large round nuclei with frequent crystalloids of Reinke in the cytoplasm. To our knowledge this is the first case of Leydig cell tumor of the ovary in a young girl in the Korean literature.