For the electrotherapy of refractory ventricular tachycardia the automatic implantable cardioverter-defibrillator (AICD) and antitachycardia pacemaker are available. The long-term use of antitachycardia pacing is still limited by the potential risk of acceleration to ventricular fibrillation. To combine the advantages of antitachycardia pacing with back-up defibrillation, we evaluated the use of an antitachycardia pacemaker with the automatic defibrillator. The AICD was implanted in 13 patients with a mean age of 62 years (from 46 to 75 years); six of them with recurrent ventricular tachycardia (170 +/- 16 per minute) which could reliably be terminated by overdrive pacing, received also an antitachycardia pacemaker (Tachylog 651). The underlying cardiac disease was coronary heart disease in 11 patients and cardiomyopathy in 2 cases. All patients had survived 1 to 6 cardiac arrests and had not responded to 6 +/- 1.5 antiarrhythmic drugs. For antitachycardia pacing we used burst stimulation with 4 to 6 stimuli and coupling intervals from 260 to 300 ms. During the follow-up period of 12 +/- 2 months, 83% of 744 tachycardias could be terminated by burst stimulation, according to the diagnostic data of the pulse generator. If the pacemaker failed to terminate or in case of acceleration (three patients), the automatic countershock of the AICD (5-42 per patient) restored sinus rhythm. In seven patients with high rate tachycardia, 2 to 69 AICD discharges occurred. No patient died suddenly, but three died due to underlying disease and one because of a pneumonia postoperatively. Future antitachycardia devices should be flexible with regard to detection and termination modes, combining antitachycardia pacing with back-up defibrillation.