Ventricular arrhythmias occur with increased frequency in hypertensive patients with left ventricular hypertrophy (LVH). The relationships, however, between ventricular arrhythmias and coexistent coronary artery disease, left ventricular dysfunction and left ventricular fibrosis have not been examined in hypertensive LVH. We carried out coronary arteriography on fifteen hypertensive patients with LVH and nonsustained ventricular tachycardia (greater than or equal to 3 consecutive ventricular complexes) of whom nine (60%) were free of significant (greater than 50% stenosis) coronary disease. To identify other possible correlates of left ventricular arrhythmias, 28 patients with LVH, comprising 17 with ventricular tachycardia and 11 without ventricular arrhythmias, underwent quantitative assessment of left ventricular function (angiographic ejection fraction), left ventricular mass (echocardiography), and left ventricular fibrosis (endomyocardial biopsy). Ejection fraction was not significantly different between the two groups (53 +/- 8% v 62 +/- 2%, P = NS). However, left ventricular mass was significantly greater (442 +/- 28 g v 339 +/- 34 g, P less than .05) and percentage fibrosis significantly higher (19 +/- 4% v 3 +/- 1%, P less than .001) in those patients with ventricular tachycardia. Thus ventricular arrhythmias in hypertensive patients with LVH cannot be entirely attributed to coexistent coronary disease, nor to left ventricular dysfunction, but are related to the degree of cardiac hypertrophy and subendocardial fibrosis.