Familial glucocorticoid deficiency (FGD) is an autosomal recessive syndrome with hereditary adrenocortical unresponsiveness to ACTH. After the cloning of ACTH receptor or melanocortin-2 receptor (MC-2R) cDNA, several kinds of mutations in the receptor genes have been reported. However, the apparently normal ACTH receptor gene in some affected children suggests that the etiology of FGD is heterogeneous. In this short review, we describe the recent advances in the molecular biology of ACTH receptor genes, its post-receptor signal transduction in the adrenocortical cells, and the molecular genetics of the FGD and a related syndrome, Allgrove syndrome. We also discuss that this kind of work will help us to understand better about the molecular mechanism of the glucocorticoidogenesis in the human being.