Although patients with diabetes mellitus may be afflicted by cardiomyopathy, its prevalence and nature are controversial. Studies have shown that fibrosis alters the acoustic properties of the heart in animals and humans and that the changes are detectable by cardiac tissue characterization with ultrasound. The present study was performed to characterize myocardial acoustic properties in patients with insulin-dependent diabetes to determine whether ultrasound tissue characterization could detect changes potentially indicative of occult cardiomyopathy. The magnitude of cyclic variation of myocardial ultrasound integrated backscatter and its phase delay with respect to the onset of the cardiac cycle in the septum and posterior wall of the left ventricle were measured in 54 patients with diabetes who had no overt cardiac disease. Conventional echocardiography documented normal ventricular systolic function in 96%. As compared with results in age-matched patients without diabetes studied previously, cyclic variation of integrated backscatter was reduced (4.6 ± 0.8 vs. 3.6 ± 1.4 dB; p < 0.001). In addition, delay was significantly increased (0.86 ± 0.09 vs. 0.99 ± 0.15). The primary analysis of the data focused on differences among the diabetic patients. Reduction of cyclic variation of backscatter was greatest in patients with diabetes who had neuropathy (3.2 ±1.0 dB; p < 0.001) as was the increase in delay (1.04 ± 0.16, p < 0.001 vs. values in patients without neuropathy). Retinopathy and nephropathy were associated with abnormal myocardial acoustic properties as well. Thus, abnormalities that may reflect fibrosis or other occult cardiomyopathic changes in diabetic patients without overt heart disease are readily detectable by myocardial tissue characterization with ultrasound and parallel the severity of noncardiac diabetic complications.