SUMMARYClinical studies in patients with 21‐hydroxylase deficiency congenital adrenal hyperplasia (CAH) were designed to ascertain the genetics of the salt‐wasting component of the disorder. The gene controlling aldosterone biosynthesis may not be the same gene that controls 21‐hydroxylase in the adrenal zona fasciculata. This we infer from the following clinical observations: (1) concordance for salt‐wasting is not observed in all HLA‐identical sibs with CAH; (2) the defect in aldosterone biosynthesis does not persist throughout life as does the fasciculate defect; (3) there is a significantly increased gene frequency of B40 and Bw47 in salt‐wasting CAH; (4) obligate heterozygote parents of patients with salt‐wasting CAH do not express a partial defect in aldosterone biosynthesis, as they do in the fasciculata. These observations cast doubt on the accepted concept of the autosomal recessive transmission of the glomerulosa 21‐hydroxy