The effect of intravenous procaine, 2 mg/kg/min, on the cardiovascular function of nine patients scheduled for cardiac valve replacement was studied under enflurane‐pancuronium anaesthesia. Procaine infusion was started after intubation during steady‐state anaesthesia, and continued until start of cardiopulmonary by‐pass. Systemic vascular resistance decreased steadily from 198.2±28.7 to 133.0±17.2 kPas/1 (P<0.05). A simultaneous decline in mean arterial pressure from 10.13±0.68 to 7.47±0.48 kPa was observed (P<0.01). Cardiac index, heart rate, central venous pressure, pulmonary arterial mean pressure and pulmonary capillary wedge pressure were all unaffected by procaine as well as by surgical stimulation. It is concluded that continuous procaine infusion as an adjuvant to general anaesthesia effectively abolishes the hypertensive and tachycardiac response to surgical stimulation. The limiting factor in the amount of infused procaine appears to be the hypotension caused by vasodilation, not myocardial depression or co