A major obstacle to the treatment of ovarian carcinoma is intrinsic/acquired resistance to cisplatin-based chemotherapy. The clinical significance of p53 overexpression in patients with ovarian carcinoma is still controversial. The aim of this study was to investigate the independent prognostic significance of p53 overexpression in patients with ovarian carcinoma who are treated with cisplatin. We retrospectively examined the overexpression of p53 in primary ovarian carcinoma, and its association with chemotherapeutic efficacy. One hundred and thirty four ovarian carcinomas were surgically removed from patients who received adjuvant cisplatin-based chemotherapy. Immunohistochemical analysis of p53 was performed using a DO7 antibody against the p53 protein in 134 ovarian carcinomas. The significance of p53 in the prognosis of patients with ovarian carcinomas was also examined by a survival analysis of mortality follow-up data covering the period from 1988 to 2001. Thirty-three tumors (25%) exhibited p53 overexpression. Overexpression of p53 in grade 2/grade 3 tumors was significantly higher than that seen in grade 1 tumors (P=0.0088, 0.0229). Patients with tumors who also showed overexpression of p53 had a significantly inferior response to chemotherapy compared with the patients with p53-negative tumors (P=0.04). Cox regression analysis revealed that p53 overexpression was prognostic for poor disease outcome after adjustment for FIGO stage, grade and residual tumor. These findings suggest that overexpression of p53 in ovarian carcinoma is associated with unfavorable clinical outcome in patients treated with cisplatin-based chemotherapy. Therefore, detection of p53 overexpression using the DO7 antibody may be considered as a predictive marker of chemoresistance for cisplatin in patients with ovarian carcinoma.