The purpose of this study was to describe the diagnosis, treatment, and follow-up of patients with concomitant primary ovarian and endometrial carcinomas. From a database of 339 endometrial and ovarian carcinomas, 9 patients with synchronous primary ovarian and endometrial malignancies were studied. Four patients (44%) had endometroid carcinoma in the ovaries and the endometrium, and 5 (56%) had differing histology. The mean age of the 9 patients was 55.4 ±5.1 years. Abnormal uterine bleeding was the main symptom in 4 patients (44.4%), whereas three (33.3%) presented with pelvic pain and 2 (22.3%) with ascites. All 9 women underwent total abdominal hysterectomy with bilateral salpingo-oophorectomy. In 4 cases, omentectomy and lymphadenectomy was also carried out. Peritoneal washing showed positive results for malignant cells in 4 cases. In 8 patients, chemotherapy was administered after the operation. All patients have remained alive without evidence of recurrence 5-8 years after the operation (100% 5-year survival rate). It is concluded that the frequency of synchronous primary ovarian and endometrial carcinomas is 2.6%, and the prognosis following appropriate treatment is favorable. (J GYNECOL SURG 15:127,1999) Address reprint requests to:A. Kontoravdis, M.D. 108 Kifissias Str. 115 26 Athens, Greece