Thirty-one patients with clear cell ovarian carcinoma who underwent primary surgery and postoperative therapy were retrospectively evaluated. Eighteen patients (58%) had International Federation of Gynecology and Obstetrics (FIGO) stage I disease, 3 patients (9.7%) stage II disease, and 10 patients (32.3%) stage III and IV disease. Patients with stage III and IV disease demonstrated a significantly poor prognosis compared with patients who had stage I or II disease (p < 0.01). No patients with stage III and IV disease survived 5 years. p53 protein expression and proliferative activity (PA) were studied by immunohistochemical methods using p53 molecule and antibodies to PCNA (proliferative cell nuclear antigen). Intranuclear accumulations of p53 product were observed in 15 of 31 (48.4%). On the other hand, 15 of 31 (48.4%) patients stained positively for PCNA (> or = 60% of cancer cells stained positively). Positive p53 staining and highly PA were associated with poor survival. Two patients with stage I a relapsed were positive p53 and highly PA. Accordingly, consolidation chemotherapy is necessary for patients with stage I a who are positive p53 and highly PA. Platinum-based chemotherapy for patients who had minimal residual tumor was effective, but 5 patients who had > or = 2 cm tumor burden were not effective at all. The response rate for platinum-based chemotherapy was 20% (1/5) among p53 positive, in contrast to 66.7% (4/6) among p53 negative patients. So it seems that p53 positive patients are chemoresistant.