We have previously reported that dexamethasone increased follicle-stimulating hormone (FSH) secretion via suppression of inhibin in immature female rats. In the present study, we investigated the effects of dexamethasone or triamcinolone on follicular development and ovarian functions (estradiol and inhibin secretion) in equine chorionic gonadotropin (eCG)-primed immature female rats. Dexamethasone significantly increased the number of ovulated oocytes in immature female rats treated with 5 i.u. eCG. Serum concentrationof FSH in eCG-treated female rats was increased by administration of dexamethasone or triamcinolone, showing the peak value at 9 h after its administration, although the levels of inhibin markedly decreased at that time. Serum concentrations of inhibin and estradiol in eCG-treated female rats increased at 24 h after administration of dexamethasone or triamcinolone. These results demonstrate that dexamethasone or triamcinolone increases FSH secretion, and the excess amount of FSH strongly stimulates follicular development cooperating with exogenous eCG.