Dilated cardiomyopathy (DCM) is usually diagnosed from the left ventricular functional viewpoint by the detection of dilated ventricular cavity and depressed myocardial contractility. Although histologic analysis of the myocardium no doubt provides clinically important information, it is possible only with microscopic examination of biopsy specimen of the myocardium. The objective of this particular study is to clarify the comparative values of the measures of ultrasonic tissue characterization, that is, calibrated myocardial integrated backscatter (IB) and the magnitude of cyclic variation in IB, with conventional echocardiographic parameters in assessing histologic condition of the myocardium. The magnitude of cyclic variation of IB and myocardial IB at end-diastole calibrated with the power of Doppler signals from the blood were measured in addition to conventional echocardiographic parameters in 14 patients with DCM. Calibrated myocardial IB was higher in patients with more fibrosis in the biopsy specimen of the heart tissue, whereas the magnitude of variation in IB or conventional echocardiographic parameters did not significantly correlate with a histologic estimate of myocardial fibrosis. Calibrated myocardial IB provides information about the myocardial fibrosis that cannot be assessable with conventional echocardiographic parameters. Calibrated myocardial IB and the magnitude of cyclic variation of IB are likely to reflect somewhat different acoustic properties of the myocardium