The clinical characteristics and treatment outcome of patients with primary peritoneal serous papillary carcinoma (PPSC) (n = 22) was compared with stage III-IV papillary serous ovarian carcinoma (PSOC) patients (n = 63). There were no statistically significant differences between the PPSC and PSOC patients with regard to the mean age, menopausal status, parity, ascites fluid volume, proportion of stage IV disease, and the rate of optimal debulking achieved. The median disease-free interval was 15 and 18 months; the median survival was 21 and 26 months; and the 5-year survival was 18 and 24% for the PPSC and PSOC groups, respectively. The median survival time for patients with a residual tumor > or = 2 cm was 20.5 and 24 months, and for residual tumor > or = 2 cm was 46 and 41 months, in PPSC and PSOC patients, respectively. Survival was thus better, in both groups, when residual disease at the end of the operation was < 2 cm, though this was statistically significant only for PSOC (P < 0.02). We conclude that patients with PPSC should be treated as other stage II-IV PSOC patients. Combining optimal debulking with a platinum-based chemotherapy may offer the patient the most effective treatment.