From January 1, 1984 to April 30, 1990, 38 patients were surgically found to have an intraabdominal disease resembling epithelial ovarian cancer. This diagnosis was confirmed in 31 patients; the remaining 7 met the criteria of primary peritoneal papillary serous carcinoma. Five of these were diagnosed retrospectively and two during surgery. The mean age at diagnosis was 61.2 years. Tumor histology revealed papillary serous carcinoma in six and mixed (papillary serous and papillary clear cell carcinoma) in one patient. Optimal debulking was achieved in three of seven cases (42.8%). Cisplatin-based combination chemotherapy was administered to all in the study group. Complete response was obtained in four patients, with one surviving for 76 months. The median survival in these patients was 34.5 months (range 6-76 months). Currently, three patients with complete response are alive with clinically undetectable disease. CA-125 assays were available in three cases and blood levels corroborated the clinically determined status of the disease. Tumor steroid hormone receptor status was determined in one case and revealed low levels of estrogen and progesterone receptors. To the best of our knowledge, the usefulness of CA-125 in the diagnosis, management, follow-up, and determination of tumor steroid hormone receptor status, mixed papillary serous and clear cell subtype histological patterns for primary peritoneal papillary serous carcinoma are first described in this report. It seems that this neoplasm may be treated and followed up as in epithelial ovarian cancer, obtaining long-term survival; however, the biologic behavior and management problems of this relatively new entity deserve further clinical experience.