The implications of ventricular fibrillation induced during elect rophysiologic testing are unclear. To determine the profile of patients in whom this arrhythmia occurs and to determine whether it has any prognostic value, follow‐up data were obtained on all patients in whom this arrhythmia was in duced in our laboratory during a ventricular stimulation protocol over an 18‐month period. Of 836 patients tested, 29 (27 men and 2 women) had inducible ventricular fibrillation. Most (52%) had coronary disease and 12 (41%) had suffered a prior myocardial infarction. All but 3 had some form of heart disease. Sixteen (55%) had abnormal left ventricular function. Eleven (38%) presented with spontaneous sustained ventricular tachycardia or ventricular fibrillation. Eight others had a history of nonsustained ventricular tachycardia.Follow‐up was obtained for a mean of 12 months.In spite of therapy, 2 patients died an arrhythmic death, 1 was resuscitated from ventricular fibrillation, 1 had spontaneous sustained ventricular tachycardia, 4 had inducible sustained ventricular tachycardia, 2 continued to have inducible ventricular fibrillation at second study, and 1 had recurrent syncope. Five patients had ventricular fibrillation induced on multiple occasions.Ventricular fibrillation induced during electraphysiologic study was found primarily in patients with structural heart disease and appeared reasonably reproducible. When reproducible, ventricular fibrillation appears to indicate a poor prognosis rather than an aspecific finding. The clinical profile of our poor prognosis group includes a history of prior ventricular tachycardia or ventricular fibrillation and the presence of coronary artery di