The role of cAMP in ovulation, oocyte maturation and prostaglandin production was assessed using a rabbit ovary preparation perfused in vitro. Dibutyryl cAMP (10-3, 10-4 or 10-5 mol l-1 was added to the perfusate of one ovary. The contralateral, control ovary was perfused with medium alone. Thirty minutes after the onset of perfusion, 50 iu hCG was added to the perfusate of all ovaries. Dibutyryl cAMP inhibited hCG-induced ovulation in a dose-related fashion. No difference in ovum maturity or degeneration was found between control ovaries and ovaries treated with dibutyryl cAMP. Ovarian progesterone production was not affected by exposure to dibutyryl cAMP. The concentrations of 6-keto PGF(1α) (the stable metabolite of prostacyclin) and PGF(2α), in the perfusate of ovaries treated with dibutyryl cAMP were 49.6% and 32.0% of the control values, respectively, 12 h after hCG administration. Inhibition of 6-keto PGF(1α) production by dibutyryl cAMP was dose related. Production of PGE2 was unaffected by dibutyryl cAMP. These data raise the possibility that continuous exposure to dibutyryl cAMP may inhibit hCG-induced ovulation in the perfused rabbit ovary via a reduction in PGF(2α) and prostacyclin production.