An unusual case is presented in which an atrioventricular (A-V) junctional tachycardia at a rate of 285 beats/min developed in the immediate postoperative period following surgical repair (a Mustard procedure) of transposition of the great vessels in a four-month-old infant. With that heart rate the systolic blood pressure bacame 35-40 mm Hg and urinary output ceased. Ventricular paired pacing was employed successfully to halve the mechanically effective ventricular rate. This resulted in a clinically effective blood pressure and return of normal urinary output. The clinical course of the A-V junctional tachycardia, plus its response to several interventions, suggested that the mechanism of the A-V junctional tachycardia was automatic rather than re-entrant. The study demonstrates that ventricular paired pacing for the control of cardiac arrhythmias is a useful clinical technique in selected cases.