Cyclic variation of integrated backscatter (CVIBS) is altered in adults with myocardial infarction, allograft rejection, and cardiomyopathy. Its utility in children has not been tested. We studied 99 normal subjects: 16 fetuses, 13 newborns, 47 children, and 23 teenagers. Fifteen children with cardiomyopathy (13 dilated and two infiltrative) were studied to define abnormal CVIBS. CVIBS was measured in the anterior septum and the left ventricular posterior wall from a two-dimensional ultrasound image with an acoustic densitometry software package. CVIBS was similar in the anterior septum (3.7 +/- 1.9 dB) and the posterior wall (4.1 +/- 2.4 dB) of all children after birth. CVIBS was significantly lower in the fetus (septum: 2.8 +/- 1.6 dB) and in children with cardiomyopathy (septum: 0.6 +/- 1.6 dB, dilated; -1.2 +/- 4.2 dB, infiltrative; p < 0.01). Four children, studied after recovery from cardiomyopathy, had diminished CVIBS despite the return of normal systolic function. The pattern and extent of CVIBS in children is similar to that of adults. CVIBS is diminished in children with cardiomyopathy.