Mibefradil is a T-type and L-type calcium channel blocker (CCB) released in the United States in 1997 for management of hypertension and chronic stable angina. Postmarketing surveillance revealed a potential serious interaction between mibefradil and beta-blockers, digoxin, verapamil, and diltiazem, especially in elderly patients. The manufacturer voluntarily withdrew mibefradil on June 8, 1998. We describe 4 cases of cardiogenic shock in patients taking mibefradil and beta-blockers who began taking dihydropyridine CCBs. One case resulted in death; the other 3 survived episodes of cardiogenic shock with intensive support of heart rate and blood pressure. Physicians who are preparing to switch patients' medications from mibefradil to other antihypertensive agents should be aware of these potentially life-threatening drug-drug interactions.