Folliculogenesis is a complex process involving dramatic morphological and functional changes in granulosa and theca cells. This process is sequential and dictated specifically by tightly regulated response to endocrine hormones and intra-ovarian regulators. In mammalian ovaries, only a few number of presented follicles in a fetal ovary can reach ovulatory status during follicular development; more than 99% of the follicles in the ovary undergo a degenerative process known as "atresia" induced by apotosis. It is characterized by distinct biochemical and morphological changes such as DNA fragmentation, plasma membrane blebbing and cell volume shrinkage. Apoptosis in ovary is regulated by a number of endocrine, locally produced intracellular mediators in a stage-specific and time-dependent manner. New knowledge of hormones and cell factors which regulate granulosa cell or oocyte apoptosis and their possible signaling pathways underlying intracellular events has made important contributions in advancing our understanding mechanism of follicular atresia.