This study assesses the effects of early and late reperfusion of the infarct-related coronary artery and collateral circulation developed after infarction on left ventricular morphology and function in 22 patients with a first acute anterior myocardial infarction and without long-standing preinfarction angina. The patients were categorized into 4 groups: group A-5 patients with successful reperfusion within 6 h after the onset of infarction: group B-6 patients with late patency of the infarct-related coronary artery; group C-6 patients without recanalization of the infarct-related coronary artery who had good collateral circulation (collateral index (CI) = 2 or 3); and group D-5 patients without recanalization who had either poor or no collateral circulation (CI = 0 or 1). The left ventricular size and function were evaluated by means of contrast left ventriculography during the chronic stage of infarction. The left ventricular global and regional functions were preserved better (p < 0.05) in group A than in the other three groups. Although there was no difference in regional wall motion of the infarct area among groups B, C and D, the ejection fraction was greater (p < 0.05) and the percentage perimetric circumference was smaller (p < 0.05) in groups B and C than in group D. Among the 4 groups, the left ventricular end-diastolic volume index tended to be greater in group D. Thus, these results suggest that blood supply to the infarct area is essential for the preservation of left ventricular size and function regardless of the timing and route.