We reviewed 53 high-grade carcinomas of the ovary in order to define pathologic features that correlate with prognosis. All tumors were Stage III with comparable amounts of residual tumor left after the primary resection. Similar postoperative chemotherapeutic regimens were given to each patient, and there was a clinical followup of at least four years in each case. The tumors were classified according to their predominant (greater than 50%) histology as transitional cell carcinoma (TCC) (18 tumors), papillary serous (18), undifferentiated (8), or endometrioid (3). There were six mixed carcinomas without predominant histology. In 17 of 18 patients, TCC predominant tumors responded completely to chemotherapy and 15 of 18 patients (83%) are alive without disease 4 to 10 years after presentation (average 6.8 years). In comparison, tumor progression/recurrence developed in 31 of 35 non-TCC tumors (18 serous, eight undifferentiated, one endometrioid predominant, and four mixed carcinomas). Of these 35 patients, 27 (77%) died of disease from 6 months to 7 years after presentation (average 2.5 yrs.). Flow cytometric determination of DNA content and immunoperoxidase studies did not allow discrimination between the histologic types of high-grade ovarian carcinomas. We conclude that TCC should be recognized as a distinct histologic type of ovarian carcinoma because of the favorable response to chemotherapy and improved patient survival.