Butylaminohydroxypropoxyphenoxymethyl methyloxadiazole was used in prehospital treatment of 40 patients (15 women, 25 men aged 63+/-17.1 years) with complicated hypertensive crises (HC) characterized by acute involvement or high risk of progression of damage of internal organs. The drug was administered as intravenous bolus injection of 10-50 mg (1-5 ml of 1% solution) under control of arterial pressure (AP) and heart rate (HR). The patients noted alleviation of symptoms by 15th min and disappearance of main manifestations of HC by 30th min. Systolic and diastolic AP were significantly lowered from baseline 190.0+/-24.4 and 105.0+/-13.5 mm Hg to 153.3+/-20,1 and 85.0+/-12,6 mm Hg, respectively. Mean dynamics of lowering of systolic and diastolic AP was 19.5 and 19%, respectively. This was accompanied by 15.4% lowering of HR (from 90.3+/-12.0 to 76.4+/-9.4 bpm). Myocardial ischemia in those patients who had it diminished or disappeared. Thus in patients with complicated HC the study drug exerted effective antihypertensive and antiischemic actions. It was well tolerated and did not cause significant side effects.