OBJECTIVE To evaluate the efficacy and safety of intravenous hydralazine in arterial hypertension. METHODS 12 patients, mean age 45.33 +/- 15.82.8 men and 4 women all of them with systolic (S) arterial pressure (AP) greater than or equal to 180 and or diastolic (D) greater than or equal to 126 mmHg with symptoms like headache, in characteristic thoracic pain and others but without an hypertensive emergency neither acute manifestation of hypertensive encephalopathy through fundi examination were studied. The AP was taken 10 minutes after rest (initial) and 5, 15, 30 and 60 min (final) after intravenous administration of hydralazine-HCL (5 mg) which was repeated when at least 20% AP reduction was not achieved. RESULTS The initial and final SAP, DAP and heart rate (HR) were 208 +/- 19.4 and 176 +/- 17.2 (p less than 0.0001), 133 +/- 11.3 and 112 +/- 11.5 (p less than 0.001) and 72 +/- 12.9 and 80 +/- 15.5 (NS), respectively. Side effects related to the drug were observed in 3 (25%) patients. One had symptomatic orthostatic hypotension, the second had precordial pain with ST-T changes compatible with myocardial ischemia and the third presented a thorax and abdominal cutaneous erythema, but all of them reversible. CONCLUSIONS Intravenous hydralazine-HC1 is an alternative when rapid arterial pressure reduction is needed.