To determine whether nitroglycerin is just as effective as nifedipine in lowering the blood pressure in excessive hypertension and hypertensive crisis, two groups of 20 patients received in random sequence either 1.2 mg of nitroglycerin sublingually or a 10 mg nifedipine capsule, which was chewed and swallowed. The blood pressure fell after 5 min in the nitroglycerin group from 211/122 mm Hg to 171/95 mm Hg and after nifedipine from 210/118 to 185/102 mm Hg. The greater effect of nitroglycerin results from faster absorption through the oral mucosa than through the small intestinal mucosa where nifedipine is primarily absorbed. After 15 to 20 min a satisfactory reduction in blood pressure was reached in both groups: 157/91 and 158/92 mm Hg, respectively. After 30 min the heart rate in the nitroglycerin group had decreased from 83 to 80/min, but in the nifedipine group it had increased from 84 to 90/min. The reduction in blood pressure persisted up to 6 h. No significant difference in side-effects was determined. Since a hypertensive crisis is usually accompanied by left-ventricular failure, pulmonary edema or angina pectoris and infarction, and nitroglycerin has been definitively shown to positively influence these conditions, preference should be given to nitroglycerin in the treatment of hypertensive crisis.