Incubation of bovine luteal cells with an atrial natriuretic peptide (rat atriopeptin II, rAP-II) did not affect hCG-stimulated or basal cyclic AMP accumulation and progesterone production, but cyclic GMP formation was stimulated by rAP-II in a dose-dependent manner, being maximally stimulatory in the nanomolar range. This stimulatory influence of rAP-II on cyclic GMP formation results from a specific stimulation of particulate guanylate cyclase. We suggest that, although rAP-II mediated cyclic GMP formation can be demonstrated in bovine luteal cells, there appear to be no acute effects of the atrial peptide on the regulation of progesterone production by these cells.