A female newborn infant with ambiguous genitalia was found to have hypertension (121/82 mm Hg) immediately after birth. The plasma testosterone (T) (0.73 nmol/l), delta 4-androstenedione (delta 4-A) (5.9 nmol/l), dehydroepiandrosterone (DHEA) (8.9 nmol/l), as well as 17 OH-hydroxyprogesterone (17 OHP) (152 nmol/l) were elevated. The diagnosis of 11 beta-hydroxylase deficiency was finally established on the basis of elevated plasma eleven-deoxycortisol (compound S) (greater than 0.6 mumol/l) and confirmed by the normalisation of the blood pressure during hydrocortisone therapy. Our case is probably the youngest patient with 11 beta-hydroxylase deficiency in whom the hypertension was found at birth.