Aldosterone production in zona glomerulosa (ZG) cells of adrenal glands is regulated by various extracellular stimuli (K+, Ang II, ACTH) that all converge on two major intracellular signaling pathways: an increase in cAMP production and calcium mobilization. However, molecular events downstream of the increase in intracellular cAMP and calcium content are controversial and far from being completely resolved. Here we found that CaMKs play a predominant role in the regulation of aldosterone production stimulated by Ang II, ACTH and cAMP. The specific CaMK inhibitor KN93 strongly reduced Ang II, ACTH and cAMP-stimulated aldosterone production. In in vitro kinase assays and in intact cells we could show that cAMP-induced activation of CaMK, using the adenylate cyclase activator forskolin or the cAMP-analog cBIMPS, was not mediated by PKA. Activation of the recently identified cAMP target protein Epac by 8-pCPT-2'-O-Me-cAMP had no effect on CaMK activity and aldosterone production. Furthermore, we provide evidence that cAMP effects in ZG cells do not involve calcium or MAPK signaling. Our results suggest that ZG cells, in addition to PKA and Epac/Rap proteins, contain other as yet unidentified cAMP mediator(s) involved in regulating CaMK activity and aldosterone secretion.