Sloan-Kettering virus gene, a product of a cellular protooncogene c-Ski is a unique nuclear pro-oncoprotein and belongs to the Ski/Sno proto-oncogene family. The aim of the present study was to locate Ski protein in rat ovaries in order to find insights into the possible involvement of Ski in follicular development and atresia. Ovaries obtained on the day of estrus were subjected to immunohistochemical analysis for Ski and PCNA in combination with TUNEL. Ski was expressed in granulosa cells that were positive for TUNEL, but negative for PCNA, regardless of the shape and size of the follicles. Expression of Ski in (TUNEL)-positive granulosa cells, but not in (PCNA)-positive granulosa cells, was verified in immature hypophysectomized rats having a single generation of developing and atretic follicles by treatment with equine chorionic gonadotropin (eCG). These results indicate that Ski is profoundly expressed in the granulosa cells of atretic follicles, but not in growing follicles. Based on the present findings, Ski has maybe played plays a role in apoptosis of granulosa cells during follicular atresia.