The dystrophinopathies are a group of X-linked genetic diseases that result from dystrophin deficiency. Duchenne's Muscular Dystrophy (DMD) is the most severe dystrophinopathy, with an incidence of 1:3500 male births. Current techniques, such as strength testing, for monitoring progress of disease and therapy in DMD patients, are imprecise and physically demanding. However, ultrasound is well-suited to detect changes in structure and organization in muscle tissue in a manner that makes low demands on the patient. Therefore, we investigated the use of ultrasound to quantitatively phenotype patients with DMD. Beam-formed RF data were acquired from the skeletal muscles of nine DMD and five normal subjects using a clinical imaging system (HDI5000 w/7 MHz probe applied above left biceps muscle). From these data, images were reconstructed using B-mode (log of analytic signal magnitude) and information-theoretic receivers (Hf-receiver). Hf images obtained from dystrophic muscle contained extensive "mottled" regions (i.e. areas with heterogeneous image contrast) that were not readily apparent from the B-Mode images. The two dimensional autocorrelation of DMD Hf images have broader peaks than those of normal subjects, which is indicative of larger scatterer sizes, consistent with pathological changes of fibers, edema, and fatty infiltration. Comparison of the relative peak widths (Full width measured at 60% maximum) of the autocorrelation of the DMD and normal Hf images shows a quantitative difference between the two groups (p < 0.005, student two-tailed unpaired t-test). Consequently, these imaging techniques may prove useful for longitudinal monitoring of disease progression and therapy.