Previous reports from our laboratory indicate that ultrasonic backscatter from myocardium exhibits a cyclic variation during the cardiac cycle that is reduced sharply by ischemia, a process which impairs both systolic contraction and diastolic relaxation. These results suggest that the cyclic variation of backscatter may be related to the cyclic variation of the contractile performance of the myocardium. Because contractile performance of the left ventricle is known to exhibit regional variability, the present study was undertaken to determine whether such regional differences in contractile performance are paralleled by differences in the magnitude of the cyclic variation of ultrasonic backscatter. Measurements obtained from representative zones of three regions of the hearts of ten open-chest dogs indicate that the magnitude of the cyclic pattern of variation of backscatter parallels the regional differences in contractile performance throughout the left ventricle with the maximum variation (5.5 +/- 0.9 dB peak-to-peak amplitude) occurring at the apex, intermediate values (4.3 +/- 0.8 dB) at the midwall, and minimum (0.5 +/- 1.0 dB) at the base. These results suggest that the ultrasonic backscatter may be sensitive to the regional myocardial contractile performance.