Chronic recurrent ventricular tachycardias represent potentially life-threatening cardiac arrhythmias. We used programmed ventricular stimulation for diagnosis, therapy and control of antiarrhythmic therapy in 17 patients with recurrent ventricular tachycardia. Ventricular tachycardia could be reproducibly induced in 15 patients by programmed stimulation, QRS morphology and rate being comparable to the spontaneously occurring tachycardia. Programmed stimulation was repeated under antiarrhythmic drug therapy. Over a follow-up period of 8 months (3--13 months), the results of the acute electrophysiologic study seem to be predicting oral long-term antiarrhythmic drug therapy. Application of programmed stimulation is associated with potential risks: induction of "non-clinical" more frequent tachycardia: 3/17 pat. = 18%; acceleration of the rate of tachycardia while trying to interrupt it: 5/17 pat. = 30%; necessity of DC-cardioversion: 6/17 pat. = 35%. Despite these risks, programmed ventricular stimulation offers substantial improvement of diagnosis and control of therapy of severely symptomatic patients with suspected or documented ventricular tachycardia and/or fibrillation.