A neonatal screening for both 21-hydroxylase and 11-beta-hydroxylase deficiencies, responsible for congenital adrenal hyperplasia (CAH), has been conducted in Campania Region, Southern Italy. In 4380 neonates, aged 2-10 days, capillary blood from a heel prick was collected on microfilter paper, and 17-alpha-hydroxyprogesterone (17OHP) measured by radioimmunoassay (RIA) using a highly specific antibody (Ab A). In addition, in 295 of these samples, both 17OHP and 11-deoxycortisol (S) were measured using an anti-deoxycortisol antibody (Ab B) cross-reacting with 17OHP 100%. All results were compared with plasma 17OHP and S levels in 21 patients with diagnosed 21-hydroxylase deficiency and in 5 healthy volunteers on metyrapone test used for blocking the 11-beta-hydroxylase activity. CAH due to 21-hydroxylase deficiency was diagnosed in a female newborn. The assay, based on the antibody reacting with both 17OHP and S, is particularly suitable for wide-scale screening programs enabling the simultaneous detection of two congenital enzyme defects.