Thirty patients who developed arterial hypertension following coronary artery bypass grafting, despite sedation, were treated randomly with sodium nitroprusside (SNP), ketanserin or urapidil. All drugs significantly decreased arterial pressure. Two patients were withdrawn because hypertension failed to respond to ketanserin. Significant tachycardia was noted only in the SNP group. An increase in Q and significant decreases in systemic and pulmonary vascular resistances were seen in all groups. Following administration of SNP, (PaO2-PaO2) and Qs/Qt increased significantly, whereas PaO2 decreased significantly. Three patients were withdrawn from the SNP group because Qs/Qt was greater than 30%. (PAO2-PaO2) and Qs/Qt showed no significant changes following the administration of ketanserin or urapidil. These drugs may have advantages over SNP in the management of hypertension following coronary artery bypass surgery.