A 53-year-old man known to have Wolff-Parkinson-White syndrome suffered an acute posterior-wall myocardial infarction. Despite successful thrombolysis treatment with streptokinase he continued to have attacks of supraventricular tachycardia with angina. The ECG showed a short P-R interval and pre-excitation with positive delta waves in leads V1-6, as well as signs of re-infarction. The tachycardias could not be satisfactorily suppressed by drug treatment. Coronary angiography revealed triple vessel disease. During this investigation ventricular extrasystoles occurred which initiated orthodromic supraventricular tachycardia and angina, as well as monophasic S-T elevations in leads II, III and aVF. This provided the indication for immediate high-frequency catheter ablation left laterally at the mitral anulus after a left-lateral accessory conduction pathway had been identified. Three days later the stenoses of the circumflex and anterior interventricular branches were dilated. The patient has been free of symptoms for 3 months and can exercise up to 150 W. The tachycardias have not recurred.