The clinical and morphological aspects of 32 ovarian tumors of the type considered to be of mesonephric origin have been studied and compared with carcinoma of the endometrium and carcinomas generally considered to arise from the surface covering cells of the ovary. An origin from pluripotential surface epithelium of the ovary or displaced endometrium is supported by a variety of findings: 1. mixed histologic pattern; 2. association with endometriosis, endometrioid carcinoma, and malignant transformation of the surface‐covering cells of the ovary, and 3. histologic similarity to clear cell endometrial carcinoma and of their metastases to papillary cystadenocarcinoma of the ovary.