After 21-hydroxylase deficiency, with 243 patients from 207 families, 3βHSD2 deficiency was the next most common form of CAH, accounting for 5% of cases, and was more frequent than 11-βhydroxylase deficiency (13 patients from 8 families) and StAR protein deficiency (6 patients from 4 families). This evidence concerns the gene STAR and classic congenital adrenal hyperplasia due to 21-hydroxylase deficiency.