The simultaneous occurrence of narrow and wide QRS complex tachycardias was observed in 2 patients evaluated at our electrophysiological centers. Electrophysiological testing revealed the coexistence of two types of arrhythmia (atrioventricular nodal reentrant tachycardia and verapamil-sensitive left ventricular tachycardia) in one patient and of three types of arrhythmia (atrioventricular nodal reentrant tachycardia, ventricular tachycardia originating from the right ventricular outflow tract, and left ventricular tachycardia) in the other. Both patients underwent successful radiofrequency ablation of all the types of tachycardia.