To study whether myocardial infarction differs in patients with and without ventricular tachycardia, the hearts of 22 decreased patients with ventricular tachycardia and 21 decreased control patients were analyzed quantitatively. The hearts from the ventricular tachycardia group were heavier and more dilated than those from the control group. Histologic analysis of a representative cross section from each heart showed that the ventricular tachycardia group had larger, more solid infarcts than did the control group. The ventricular tachycardia group also had a greater area of spared subendocardium, more hydropic change of the spared subendocardium, and more 'ribbon type' spared subendocardium, which was defined as spared subendocardium of uniform contour 1 mm thick or less. The ventricular tachycardia group was divided into a subacute subgroup (n = 14, dying ≤ 10 weeks after infarction) and a chronic subgroup (n = 8, dying > 10 weeks after infarction). The infarcts of the subacute ventricular tachycardia group were more solid and had a greater amount of ribbon type spared subendocardium than those of the chronic ventricular tachycardia group. This information can serve as a baseline for the evaluation of animal preparations of tachycardia and, when combined with knowledge of the location of the arrhythmogenic region furnished by intraoperative mapping, should lead to better understanding of the anatomic substrate for ventricular tachycardia.