Progress has been made in identifying the molecular changes that occur in ovarian carcinoma; still our understanding of these changes and their interactions remains incomplete. In the present study the authors examined the expression of retinoblastoma protein, a tumor suppressor protein, in a spectrum of ovarian epithelial tumors including cystadenomas, low-malignant-potential tumors, and carcinomas. A heterogeneous pattern of reactivity was observed in all of the cystadenomas, in all of the low-malignant-potential tumors, and in a majority (27/34) of the carcinomas. The remaining carcinomas showed either a complete absence of reactivity or a pattern of altered reactivity characterized by areas of tumor with intact reactivity adjacent to zones of tumor with a complete absence of reactivity. There was no significant association between grade or stage and absent/altered reactivity. We conclude that alterations of retinoblastoma protein expression are uncommon in ovarian carcinoma.