Despite the potential importance of c-myc protein to cell proliferation and apoptosis, nothing is known about the contribution of this proto-oncogene to the development of the ovarian follicles in humans. Therefore the localization of c-myc in the human ovary was the main aim of this study. Localization of c-myc mRNA in 15 human ovaries was assessed by in situ hybridization. Atresia of the antral follicles was determined by in situ 3'-end labeling of fragmented DNA. Proto-oncogene c-myc was found in all the stages of follicular development except the primordial stage. The corpus luteum was also positive for c-myc mRNA. There was no positive staining for c-myc in either the corpus albicans or the postmenopausal ovary. These data indicate that the expression of c-myc may play a role in the molecular mechanisms of cell proliferation and apoptosis in the human ovary.