The efficacy and safety of a new antitachycardia pacing technique, self-adapting decremental overdrive pacing, was assessed in patients with clinical ventricular tachyarrhythmias who underwent programmed ventricular stimulation and serial drug testing. The three phases of this study involved a learning/experience phase, followed by intrapatient comparison of decremental overdrive pacing with conventional antitachycardia pacing modalities of overdrive burst ventricular pacing, and diastolic scanning with single (S2) and double (S2S3) ventricular extrastimuli. The final phase involved intrapatient comparison of automated decremental overdrive pacing with overdrive burst ventricular pacing in patients with ventricular tachycardia (VT) cycle lengths of 280 msec or greater. Decremental overdrive pacing was superior to overdrive burst pacing and diastolic scanning (S2S3 and S2) (83% vs 38%, 50%, 9%) in patients with VT cycle lengths of 280 msec or greater. Automated decremental overdrive pacing as applied in the final phase was the most efficacious modality, terminating 92% of VT episodes compared with 56% for overdrive burst pacing in the same patients.