We report an adult patient with junctional ectopic tachycardia, a condition which was initially described in infants, frequently in association with congenital defects. The patient had a rapid, irregular paroxysmal junctional tachycardia with a rate ranging from 160 to 220 beats/min, distinguishing it from the more common nonparoxysmal junctional tachycardia in which a slower heart rate is seen. The electrophysiological study performed during an episode of tachycardia demonstrated periods of atrioventricular dissociation and narrow QRS complexes as well as a junctional ectopic rhythm, which was suggested by a His deflection preceding each ventricular depolarization with a normal HV interval. Both the response to exercise and the results of atrial and ventricular stimulation suggested enhanced automaticity of a high junctional focus. Therapy combining procainamide, verapamil, and digitalis proved to be effective. Thus, junctional ectopic tachycardia can also occur in adults, probably due to enhancement of automaticity.