The androgen-secreting Leydig cells produce cGMP, but the pathways responsible for generation and actions of this intracellular messenger have been incompletely characterized in these cells. Here we show the presence of mRNA transcripts for the membrane-bound and soluble guanylyl cyclases (sGC), the cGMP-specific phosphodiesterase 5, and the cGMP-dependent kinase I (PKG I) and PKG II in purified rat Leydig cells from adult animals. Stimulation of both guanylyl cyclases and inhibition of phosphodiesterase 5 in vitro was accompanied with elevation in cGMP and androgen production, whereas inhibition of soluble guanylyl cyclase and PKG led to a decrease in steroidogenesis. The stimulatory action of cGMP on steroidogenesis was preserved in cells with inhibited cAMP-dependent kinases. Experiments with exogenously added substrates revealed the dependence of cGMP-induced progesterone and androgen synthesis on cholesterol, but not on 22-OH cholesterol, pregenolone, progesterone, and ⁴-androstenedione. Treatment with nitric oxide donor increased phosphorylation of the steroidogenic acute regulatory protein (StAR). In contrast, inhibition of sGC and PKG, but not protein kinase A (PKA), significantly reduced StAR phosphorylation. These results suggest that cGMP contributes to the control of basal steroidogenesis in Leydig cells through the PKG-dependent modification of the StAR protein.