Ventricular tachycardia and accelerated ventricular rhythm presenting in the first month of life. Fourteen infants aged less than 1 month presented to our institution during the last 22 years with ventricular tachycardia (VT) or accelerated ventricular rhythm and a structurally normal heart. In 2, VT was associated with long QT syndrome. Both are alive on beta-blocker therapy, 1 with an implanted pacemaker. Twelve infants had accelerated ventricular rhythm, and 2 of these died in the first 2 months of life of unrelated conditions. The other 10 are alive at a median age of 4 years (range 2 months to 11 years), and none were lost to follow-up. Hemodynamic compromise did not occur with accelerated ventricular rhythm. The ventricular rate was very close to the sinus rate in all 12, less than 12% above the sinus rate. The mean QRS duration during accelerated ventricular rhythm was 92.5 ms, and averaged twice the QRS duration during sinus rhythm. Fusion beats were seen in all 12, and there was atrioventricular dissociation with capture beats in 10. In 2, ventriculoatrial conduction was present. Treatment was attempted in 5 of the 10 survivors with accelerated ventricular rhythm, and was thought to be successful in 4. Treatment was later successfully withdrawn in all 5, so that all 10 survivors were free of accelerated ventricular rhythm and were not receiving antiarrhythmic medications at last follow-up. Because of the excellent long-term outcome and the lack of hemodynamic compromise during the rhythm, it seems reasonable to withhold antiarrhythmic therapy in infants with accelerated ventricular rhythm and await resolution of the rhythm. 