Intravenous labetolol, a nonselective α- and β-blocking drug, is commonly used to treat severe hypertension. Nonselective β-blockers can cause hyperkalemia, especially in patients with renal failure. One series reported 3 renal transplant patients who had hyperkalemia after labetolol infusion, but none of these patients developed any serious complication. We report a case of life-threatening hyperkalemia (serum [K<sup>+</sup>] 9.9 mEq/l) with ventricular tachycardia and hypotension in a patient on maintenance hemodialysis who received labetolol for a hypertensive emergency. Physicians should be aware of this potentially lethal complication, which is easily preventable.