The ovary is one of the organs in which an intrinsic renin-angiotensin system (RAS) has been described. Among angiotensin II receptors, the angiotensin II receptor subtype 2 (AT2) is believed to play an important role in mediating or modulating a variety of intraovarian processes. Previous studies were mainly based on ligand binding techniques using AT2 receptor-specific antagonists. Despite the recent cloning of the AT2 gene, no information is available about the exact intraovarian distribution of AT2 mRNA expression. Therefore, we analyzed ovaries from sexually mature, untreated rats by nonradioactive in situ hybridzation using an AT2-specific anti-sense RNA probe. Experiments were performed on perfusion-fixed ovaries obtained from different stages of the estrous cycle. As an important finding, strong AT2 mRNA expression could be demonstrated exclusively in follicular granulosa cells. Follicles containing AT2 mRNA-positve granulosa cells were mainly in the advanced tertiary stage of follicular development, already exhibiting features of atresia. In addition, individual collapsed, definitive atretic follicles also showed strong AT2 mRNA expression solely in granulosa cells. In corpora lutea and in other structures of the ovary, no message for the AT2 receptor could be detected under these conditions. These data may contribute to a better understanding of the effects exerted by an intraovarian RAS. (J Histochem Cytochem 46:865-870, 1998)