This is the first reported case of the idiopathic type of primary aldosteronism in pregnancy. The severely hypertensive patient was unresponsive to treatment with high doses of four antihypertensive agents administered concurrently. A drastic improvement in blood pressure was noted within 24 hours of beginning enalapril maleate, although subsequent deterioration in fetal status led to delivery at 26 weeks' gestation. Alternatives to standard medical therapy may be necessary for this rare but potentially life-threatening disease during pregnancy.