The Brenner tumor of the ovary has been the topic of voluminous clinical and pathologic literature since its original description by Macnaughton-Jones in 1898. One of the major problems confronting most investigators of this uncommon neoplasm has been the question of histogenesis. There is general agreement that the tumor is derived from surface (coelomic) epithelium, as are the serous and mucinous cystadenomas. Most Brenner tumors are asymptomatic except for some which have features suggestive of estrogen production. The major pathologic variants are the proliferating and the malignant Brenner tumors; a poor prognosis is associated with the latter neoplasm. Approximately 30% of all benign Brenner tumors have a second histologic type of tumor in the ipsilateral or contralateral ovary, a serous or mucinous cystadenoma in most cases. Brenner tumors have also been reported in the broad ligament and in the testis on rare occasions.