Abstract
Congenital adrenal hyperplasia because of 21-hydroxylase deficiency is closely linked to the HLA system. The lod scores in 14 informative families are presented. Apart from linkage, the 21-hydroxylase deficiency is associated with an increase of BW47 antigen and lack of B8 antigen in patients. A family with a possible recombination between the 21-hydroxylase deficiency and the HLA complex was found, thus indicating that the 21-hydroxylase gene lies outside the HLA system and is closely linked to the HLA-DR locus.