Pregnancy luteoma is composed of a single or multiple nodules of large lutenized cells that develop during pregnancy but involute during the puerperium. This lesion is usually an incidental finding at the time of cesarean section or postpartum tubal ligation. Microscopically, this tumor is difficult to be differentiated from various types of sex-cord stromal tumors including Leydig cell tumor, luteinized thecoma, adult or juvenile granulosa cell tumors with luteinization, and lipoid cell tumor. We report a case of pregnancy luteoma in a 34-year-old primipara without virilizing symptoms at the time of cesarean section in the right ovary. The mass measured 5x4.5x3.5 cm and 60 gm in weight. The cut surface was homogeneously yellow-orange with mulitple hemorrhagic spots. Microscopically, the tumor revealed solid, trabecular, or microcystic pattern of large granular eosinophilic luteinized cells and somewhat large nuclei with prominent nucleoli. Differentiation from Leydig cell tumor and juvenile granulosa cell tumor was difficult in this case.