Calretinin is a calcium-binding protein which is primarily expressed by certain cells of the nervous system, both central and peripheral. Its presence in nonexcitable cells has been little studied. Using a polyclonal antibody and paraffin sections we have analysed the presence of calretinin in the human ovary of different ages, and in polycystic ovaries. Our results revealed the selective presence of calretinin, specifically localised in the cells of the germinal epithelium, those of the theca interna and the theca lutein cells, in the cells of the neurovaso-epithelial association and of the canalicular structures of the mesovarium. Calretinin was also present in a few cells of the theca externa and some interstitial cells. No appreciable quantitative differences in the strength of the positive reaction were seen between the ovaries of different ages or between the normal and the polycystic ovaries. The presence of calretinin was confirmed by western blot analysis. The selective presence of calretinin in the human ovary, in androgenic cells and in the cells of the germinal epithelium is discussed in relation to its possible function as a Ca2+ buffer