Two brothers with Fabry's disease presenting with palpitations were found to have intermittent supraventricular tachycardias. Their electrocardiograms, when symptom-free, revealed short PR intervals consistent with ventricular pre-excitation. Treatment of one of the brothers with verapamil resulted in improvement of the palpitations and reduction in frequency of the tachycardia. Recurrent supraventricular tachycardia associated with ventricular pre-excitation has not previously been described in Fabry's disease. Evidence suggests that this complication may be due to glycolipid deposition in the conducting system around the atrioventricular node.