Labetalol, an antihypertensive agent that blocks both beta- and alpha-adrenergic receptors, was administered intravenously to 19 patients with accelerated hypertension who required rapid lowering of blood pressure. Systolic blood pressure was lowered from 209 +/- 4 to 143 +/- 2 mm Hg; diastolic blood pressure was reduced from 140 +/- 2 to 93 +/- 2 mm Hg. Side-effects were minimal and included nausea, epigastric burning, rhinorrhea, and premature ventricular contractions. One patient became hypotensive and required treatment. Overall, the study demonstrates labetalol to be a safe and effective agent for the emergency lowering of blood pressure, with demonstrated results comparable to other parenteral agents.