Mutation of the p53 gene and activation of c-erbB2 oncogene are common in human ovarian carcinomas; however, their role in the early development of ovarian cancer is unclear. Twelve ovarian cystadenomas, five borderline tumors and eleven invasive carcinomas were studied for p53, c-erbB2 and proliferating cell nuclear antigen immunoreactivity using an immunohistochemical technique. While none of the 11 benign cytadenomas were reactive for p53, c-erbB2 or proliferating cell nuclear antigen, all 5 borderline tumors demonstrated focal and all 11 invasive carcinomas revealed diffuse immunoreactivity for the monoclonal antibodies studied. Our results suggest that benign ovarian epithelial tumors are distinct lesions from the borderline and malignant ovarian tumors and both c-erbB2 and p53 may have a role in malignant progression from precursor lesions.