Fourteen patients with transmural myocardial infarction were studied by gated cardiac blood pool scanning (to determine regional ventricular function) and 43-K myocardial imaging (to determine the regional distribution of myocardial perfusion). An akinetic area on the gated scan and an area of decreased tracer concentration on the 43-K image were detected. The area of reduced 43-K concentration averaged 33.5% of the left ventricular circumference which correlated (r = 0.74, p less than 0.01) with the area of infarction determined by the zone of akinesis, 34.2% of left ventricular circumference. The extent of akinesis and left ventricular ejection fraction were significantly different in those patients with left ventricular failure than in those without failure.