An essential role of ACTH is to assure that optimal steroidogenic capacity is maintained in the adrenal cortex throughout life. This is achieved by maintaining transcriptional pressure on the genes encoding the adrenocortical steroid hydroxylases via the second messenger, cAMP. Even though these genes respond coordinately to cAMP, it has been surprising to discover that each gene uses its own unique cAMP response system during this coordinate response. Thus, different cis elements and sets of transcription factors control the cAMP responsiveness of each different steroid hydroxylase gene. Although the physiological basis of this diversity in biochemical mechanisms of transcriptional regulation is not apparent, a portion of this signaling pathway is common to all of these genes. In particular, the action of cAMP-dependent protein kinase and an as yet uncharacterized cycloheximide-sensitive step are necessary for ACTH-mediated transcription of each gene. Biochemical characterization of these common steps in the ACTH-dependent signaling pathways is essential to an understanding of the maintenance of optimal steroidogenic capacity in the adrenal cortex.