AIMS Ventricular tachycardia spreading from the anterior or posterior division of the left bundle branch is generally called fascicular tachycardia (FT). We will present our experience with FT, a type of ventricular tachycardia not necessarily implying the absence of heart disease and/or sensitivity to selective antiarrhythmic drugs, but only particular routes of left ventricular depolarization. METHODS Since 1981 we have had the opportunity to study 10 cases of FT (nine men and one woman; aged 28-77 years, mean ± SD 55 ± 18.6 years) by means of echocardiography, coronary angiography (seven cases), endomyocardial biopsy (five cases), signal-averaged electrocardiogram (SAECG, nine patients), electrophysiological and electropharmacological evaluation. RESULTS Seven patients had paroxystic, extrastimulus inducible FT that was sensitive to verapamil given intravenously (group A); three patients, on the other hand, showed repetitive or incessant FT, not modifiable by stimulation techniques and sensitive to class 1 antiarrhythmic drugs (group B). Patients presented histologic substrates ranging from the absence of heart disease to previous myocardial infarction or myocarditis. FT spontaneously disappeared within 2 years in group B, while frequently persisted in the long term in group A. CONCLUSIONS FT is not a homogeneous group of ventricular tachycardia, as patients may differ according to clinical presentation, mechanisms that are involved in the genesis of the arrhythmia and natural history; the histologic substrate is highly variable, ranging from the total absence of heart disease to severe forms of myocardial involvement.