We applied transcoronary chemical ablation of the atrioventricular (AV) node to a patient with uncontrollable paroxysmal supraventricular tachycardia (PSVT). Through an angioplasty dilatation catheter. 99% ethanol at a dose of 1.0 ml was selectively infused into the AV nodal artery. Complete AV block with junctional escape rhythm occurred. Two weeks later, the treadmill exercise test was performed according to a modified Bruce protocol. The patient tolerated for 12 min, and the heart rate increased to 85 beats/min. His bundle electrocardiogram showed that the AV block resulted from atrio-Hisian block. Neither atrial nor ventricular extrastimulus could induce the tachycardia. It appeared that chemical ablation was a good method for controlling medically resistant PSVT. Elevation of serum creatine kinase was observed when ethanol overflowed during the ablation procedure. Occlusion of branches of the AV artery and mild hypokinesis in the inferobasal wall of the left ventricle were seen.