Prompted by reports of hypotension with myocardial ischemia after bolus injection, we restudied the efficacy of diazoxide infusion (5 mg/kg, rate, 15 mg/min) in 35 hypertensive patients. In 20 patients with chronic hypertension, mean arterial pressure of 138 mm Hg was 110 (after 30 min) and 121 (after 8 hr). In 15 patients with hypertensive crisis, there was a fall from 159 to 126 (in 30 min) and 133 mm Hg (after 8 hr), similar to findings in 12 patients with hypertensive crisis treated with a 300-mg bolus injection (159, 130, 140 mm Hg). In the latter, the maximal systolic blood pressure decrease was greater (56 mm Hg, reached in 4 min) than in the 15 patients with hypertensive crisis treated by slow infusion (38 mm Hg in 28 min). Thus, infusion of diazoxide causes a gradual decline of blood pressure and is, in contrast to current opinion, also an effective treatment in hypertensive crisis.