Since overexpression of mutant p53 protein is a common feature of invasive epithelial ovarian cancers, we investigated whether overexpression of the p53 tumor suppressor gene product occurs in benign and borderline epithelial ovarian tumors. Immunohistochemical staining for p53 was performed in frozen samples of 17 benign tumors and in 49 borderline tumors (4 frozen, 45 paraffin embedded). Overexpression of p53 was observed in 0/17 (0%) benign ovarian tumors and 2/49 (4%) borderline tumors. Overexpression of p53 in borderline tumors was only seen in advanced stage cases; overexpression was seen in 2/8 (25%) stage III cases, but not in any of 41 stage I/II cases. In conclusion, overexpression of p53 is not a feature of benign epithelial ovarian tumors or early-stage borderline ovarian tumors. Similar to invasive epithelial ovarian cancers, however, a fraction of metastatic borderline tumors also overexpress p53.