A case of coronary artery spasm during a non-cardiac surgical procedure is presented. Two paroxysmal episodes of ST segment elevation in lead 11 and aVF without changes in V5 developed during general anaesthesia. These changes were not preceded by increases in heart rate or arterial pressure. The second episode was associated with a ventricular bigeminal rhythm. This case demonstrates the importance of monitoring several leads in patients likely to develop peroperative spasm of the coronary arteries. Intravenous nitroglycerin was effective in treating the second episode of coronary artery spasm. However, this episode occurred in spite of nitroglycerin administered intravenously at a rate of 0.25 microgram/kg min.