The molecular mechanisms involved in the regulation of expression of the rat CRH gene have been examined in rat pheochromocytoma (PC-12) cells transiently transfected with a chimeric gene containing 1.4 kilobases of rat CRH 5'-flanking DNA fused to the bacterial reporter gene encoding chloramphenicol acetyltransferase. Cyclic AMP analogs and activators of adenylate cyclase positively regulate the expression of this chimeric gene in PC-12 cells, inducing chloramphenicol acetyltransferase activity more than 15-fold. The DNA sequence required for this response to cAMP has been localized to a 59 base pair region located between 238 and 180 base pairs 5' to the putative CRH mRNA cap site. This sequence can confer cAMP-responsiveness on a heterologous promoter in an orientation independent fashion and has homology to cAMP regulatory regions from a number of other eukaryotic genes.