Hypertension associated with tachycardia, elevated filling pressures and increased systemic vascular resistance occurs in 30-60% of patients recovering from coronary artery surgery (1,2). It is usually present when the patients arrive from the operating room in the intensive care unit (ICU), or develops in the first two hours postoperatively. Traditionally sodium nitroprusside (S) is the drug of first choice for the i.v. treatment and prevention of hypertension and increased filling pressures developing after coronary artery surgery (CAS). Its major disadvantage is reflex tachycardia associated with increased myocardial oxygen consumption. Urapidil (U) has both peripheral alpha-1-adrenoreceptor blocking activity and a central antihypertensive effect at the level of the 5HT-1A serotonergic receptor, resulting in enhanced peripheral sympathetic inhibition (3,4). Informed consent and institutional approval for the study were obtained. When mean arterial blood pressure (MAP) increased above 90 mmHg within the first 2 hours after CAS, 53 patients were randomly allocated to one of two groups. 25 patients received U (bolus of 25 mg; initial infusion rate of 15-85 micrograms/kg/min; maintenance infusion rate of 2-7 micrograms/kg/min) and 28 patients received S (initial infusion rate of 1-2 micrograms/kg/min; maintenance infusion rate of max. 5 micrograms/kg/min). The infusion rate was then adjusted to maintain MAP between 80 and 90. Measuring points were: 1. baseline; 2. 30 min after starting the infusion; 3. 60 min after starting the infusion; and at 2 hour intervals thereafter until the next morning.(ABSTRACT TRUNCATED AT 250 WORDS)