Interrenal and ovarian tissues of Rana esculenta were incubated in vitro during the preovulatory, ovulatory and postovulatory phases to study the basal release of prostaglandin E2 (PGE2), prostaglandin F2 alpha (PGF2 alpha), corticosterone, and cortisol. The effects of exogenous PGE2 and PGF2 alpha on interrenal and ovarian corticosteroid release were also studied. In addition, the plasma values of these four hormones were assessed during the same phases. During in vitro interrenal incubations, PGE2, PGF2 alpha, corticosterone, and cortisol basal releases were higher in the postovulatory phase, PGE2 and PGF2 alpha treatment in vitro increased corticosteroids during the ovulatory phase. During in vitro ovarian incubations, PGE2 basal release was higher in the preovulatory phase and PGF2 alpha and corticosteroids in the ovulatory phase; PGE2 treatment in vitro decreased corticosteroids in the ovulatory phase, and PGF2 alpha increased corticosteroids in the preovulatory and postovulatory phases. PGE2, corticosterone and cortisol plasma values were higher during the postovulatory phase, while PGF2 alpha was elevated during the ovulatory phase. These findings suggest that ovarian corticosteroids could be considered one of the factors inducing ovulation and that their synthesis may be modified by PGs.