The authors studied the influence on recurrence and mortality of induced ventricular arrhythmias during electrophysiological studies performed to assess the efficacy of treatment of sustained monomorphic ventricular tachycardia. One hundred and twenty-six consecutive patients investigated from 1981 to 1988 were included. The underlying pathology was chronic myocardial infarction (N = 56), dilated cardiomyopathy (N = 24), right ventricular dysplasia (N = 31) and there were 15 idiopathic cases. All these tachycardias could be induced during the control study. A second test was performed after instituting treatment. This was maintained whatever the result of the electrophysiological study except in patients in whom the tachycardia rate was over 130/mn and/or poorly tolerated. Recurrences were defined as the observation of tachycardia with the same morphology and/or the occurrence of sudden death. Follow-up averaged 29 +/- 21 months. The absence of recurrence and survival were assessed by the Kaplan-Meier method and Logrank's test. It was not possible to induce any arrhythmia after treatment in 52 patients (41%). The prevalence of absence of recurrence in this group was 0.863. If the induction of ventricular fibrillation, doublets or short runs of VT (N less than 6 with no recurrences) are included, the value increased to 0.877. These patients were considered to be non-inducible. The prevalence of absence of recurrence of arrhythmia in patients in whom it was possible to induce sustained ventricular tachycardia of the same morphology as the clinical arrhythmia was 0.512 (p = 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)