We report four ovarian granulosa cell tumors of the adult type containing small foci of hepatic cell differentiation. The patients ranged in age from 35 to 54 years and had unilateral adnexal masses. The smallest tumor was 4.0 cm in diameter and the largest, 11.0 cm in diameter. Three tumors were solid and cystic, and one was cystic. Microscopic examination showed typical patterns of adult granulosa cell tumor, with the additional finding of scattered islands of large cells with abundant eosinophilic, slightly granular cytoplasm and central round nuclei containing single prominent nucleoli. Bile pigment was detected in canaliculi between some of the large cells in three tumors. The hepatic cells were positive immunohistochemically for cytokeratin (CAM 5.2) and epithelial membrane antigen in two cases and alpha-fetoprotein in one of two cases. Carcinoembryonic antigen was stained in a canalicular pattern in two cases. Staining for vimentin and alpha-inhibin was negative. Liver cells in granulosa cell tumors must be differentiated from Leydig cells, which are found very rarely in granulosa cell tumors, and luteinized stromal and granulosa cells, which are present more commonly in these tumors; all three of the latter cell types are positive for alpha-inhibin.