We performed a multicentre, phase IV, open-label clinical trial to examine the clinical usefulness of a continuous infusion of nicardipine hydrochloride to control hypertension in 31 patients with acute aortic dissection. Target blood pressure levels were reached within 15 min in 16 patients; in 15-30 min in 10 patients; in 30-45 min in three patients; and in 45-60 min in two patients. Baseline average systolic, diastolic and mean arterial blood pressures were 147 +/- 23 mmHg, 82 +/- 18 mmHg and 104 +/- 18 mmHg, respectively, with third-day pressures significantly reduced at 119 +/- 12 mmHg, 69 +/- 9 mmHg and 86 +/- 8 mmHg. Blood pressures after discontinuation of the infusion were not significantly different from those measured on the third day of infusion and no definite adverse effects attributable to the treatment were observed. Nicardipine hydrochloride was both effective and safe at controlling blood pressure in patients with acute aortic dissection.