The authors report the first case of adrenergic ventricular tachycardia observed in two 11 year old homozygotic twins. Syncope on exercise led to the investigation of the first twin with confirmation of the diagnosis by exercise stress testing. The same investigations led to the demonstration of the condition in the second asymptomatic twin. The two patients were treated with nadolol and there has been no recurrence of syncope with a 2 year follow-up. Adrenergic ventricular tachycardia is a rare arrhythmia with a risk of sudden death which may be prevented by betablocker therapy. An exhaustive familial inquiry is essential, but is only positive in one out of three cases. Mutations in the ryanodine receptor gene (hRyRZ) and also in the calsequestrin gene (CASQ2) have recently been reported. Progress in the understanding of the genetics of this condition should improve primary preventive measures.