Tissue characterization previously identified ischemia, infarction, and cardiomyopathy in animal myocardium. Investigations to determine whether analogous results occur in patients were undertaken with a real-time two-dimensional backscatter imaging system. Remote infarction in 15 patients was accompanied by reduced magnitude and delayed cyclic variation. Similarly, ultrasonic evidence of diminished contractile function was found in five patients with dilated cardiomyopathy compared to 15 patients in a control group. Studies of 15 patients with acute myocardial infarction indicate that tissue characterization may permit the detection of reversibly injured or 'stunned' myocardium, despite the presence of severe wall-motion abnormalities that might otherwise mask the presence of viable but transiently dysfunctional tissue.