The authors report their findings in 47 cases of ventricular arrhythmias due to arrhythmogenic dysplasia. The 47 patients were selected on the presence of ventricular tachycardia or fibrillation associated with dysplasia affecting selectively (44/47) or predominantly (3/47) the right ventricle at angiography. In this series males were predominant (38/47, 81 p. 100), familial incidence was high (13/47, 28 p. 100) and ECG abnormalities were constant. Most of the dysrhythmias (40/47) consisted of sustained ventricular tachycardia (VT) with left bundle branch block pattern (96 p. 100), occurring at the rate of 1.6 per patient on average and seldom with extreme axial deviation, as seen in post-infarction VT or VT associated with cardiomyopathy. The QRS complex was slightly prolonged (151 +/- 28 ms) and of high amplitude (2.5 +/- 1 mV on a VR, a VL and a VF leads), these values being intermediate between those of mild VT bursts and those of post-infarction or cardiomyopathy-related VT. The tachycardia was easily tippered by EP study, Intercritical Holter recordings showed frequent ventricular extrasystoles in the vast majority of cases; these were usually polymorphous and grouped into short bursts in one-half of the patients. On an 8.3 +/- 7 years' follow-up starting with the first attack of VT, it was found that only during the initial phase the spontaneous onset of VT was mediated by the adrenergic system (triggered by sports). Only 3 patients died during the follow-up period: one of ventricular fibrillation, 2 of right heart failure.(ABSTRACT TRUNCATED AT 250 WORDS)