This study determined the cardiovascular effects of percutaneous radiofrequency coagulation of the Gasserian ganglion, performed under neuroleptanalgesia and intermittent ultrashort-acting barbiturate anaesthesia. Twelve ASA physical status class II patients were studied. Highly significant increases in mean heart rate and arterial blood pressure followed the insertion of the cannula electrode into the Gasserian ganglion (p less than 0.001). In six randomly assigned patients severe tachycardia and hypertension also accompanied the progress of the thermal lesion (p less than 0.0001). Three patients developed premature ventricular contractions, and two developed significant ST segment depression. Intravenous nitroglycerin, used during current generation, successfully controlled the hypertensive response in the other six patients. In percutaneous thermocoagulation of the Gasserian ganglion the patient's co-operation is essential. In addition to providing suitable operating conditions for both surgeons and patient, we should also be able to maintain normal and stable cardiovascular haemodynamics. Intravenous nitroglycerin used as an adjunct to light general anaesthesia safely maintained intraoperative normotension. It is also suggested that patients with coronary artery disease be adequately monitored and protected during the procedure.