Ambiguous genitalia in the newborn, often in combination with severe salt wasting, is the clinical hallmark of 21-hydroxylase deficiency. The pathophysiology of CAH can be traced to an inherited defect in the gene encoding the enzyme 21-hydroxylase. Treatment of patients with CAH is targeted at replacing cortisol, which is produced in insufficient quantity. With proper hormone replacement therapy, normal and healthy development may often be expected. Radioimmunoassay of serum and urinary steroid levels permit reliable diagnosis of the various forms of CAH. Prenatal treatment of affected females prevents potential sex misassignment, and repeated genital surgeries that cannot easily recreate natural genital structures. Based on our experience, proper prenatal diagnosis and treatment of CAH owing to 21-hydroxylase deficiency is safe and effective in significantly reducing or eliminating virilization in the affected female, thus making CAH one of the few monogenic disorders in which postnatal life is influenced by effective prenatal treatment. However, follow-up studies are still necessary to evaluate potential long-term consequences of prenatal treatment with dexamethasone.