Idiopathic VT originating from posteroseptal mitral annulus. We describe a 71-year-old man with a ventricular tachycardia (VT) originating from the mitral annulus. A sustained VT was induced by exercise or an isoproterenol administration, but not by pacing. Frequent premature ventricular contractions(PVCs) with the same QRS as the VT were transiently suppressed by an adenosine triphosphate injection,suggesting that it was due to cyclic-AMP mediated triggered activity. The PVCs and VT were all abolished by radiofrequency catheter ablation guided by the earliest activation and a perfect pace map, which was located at the posteroseptal mitral annulus. The patient has been free from any symptoms for 2 years.(J Cardiovasc Electrophysiol, Vol. 17, pp. 1375-1377, December 2006)