In the mannalian ovary, follicular development and stresia continuously occur during the reproductive cycles. Follicular atresia occurs through granulosa cell apoptosis. Apoptosis is known as the physiological cell death, which is regulated by bcl-2 gene family. In the vcl-2 gene family, bcl-2 and bcl-xLong are known as inhibitors of apoptosis, whereas bax and bcl-xShort are known as inducer of apoptosis. We thought that bcl-2 protein is associated with follicular development and atresia. But it is not known that the distribution of cells containing bcl-2 protein during follicular development and atresia. Therefore, to examine the distribution of cells with bcl-2 protein during ovarian follicular development and atresia. Therefore, to examine the distribution of cells with bcl-2 protein during ovarian follicular development and atresia, the immunohistochemistry was used ih the rat ovary. Bcl-2 immunorectivity was localized in the intestitial cells, theca externa cells and granulosa cells around of antrum. All positive sighals were observed in the cytoplasm of these cells. Positive sighals were strongly observed in the interstitial and theca externa cells of growing antral follicles. While, positive signals were weakly observed in these cells from atretic antral follicles. Positive sighals were very weakly observed in the granulosa cells of growing and atreticantral follicles. According to these data, we suggested that bcl-2 proteins which were wtrongly expressed in the interstitial cells and theca externa cells of growing antral folicles inhibit follicular atresia. And wer purposed that bcl-2 proteins regulated follicular development and atresia through the action of acl-2 gene family.