Clinical and pathologic features of 24 serous adenofibromas of the ovary (including 3 undergoing malignant change) are presented. These tumors are more common than allusions to them in the literature would indicate. Hormonal activity seems to be a rare occurrence, as does malignant change. Insufficient time has elapsed for us to offer information regarding the prognosis of the malignant fibro-adenocarcinoma: however, it seems likely that it will not differ greatly from that for the more common serous cystadenocarcinomas.