Histological changes of the myocardium occur with aging due to an increase in collagen content, hypertrophy of fibers, and patchy fibrosis. Quantitative analysis of conventional echocardiographic images provides an in vivo assessment of myocardial structure by the evaluation of the gray level distribution; with this technique, a relation between myocardial fibrosis and pathological ultrasonic response has been documented. The aim of this study was to evaluate the relation between ultrasonically assessed myocardial structure and age in a normal population. Seventy-eight subjects (47 men; mean age, 51 years; age range, 23-87 years) without apparent cardiovascular and systemic disease underwent conventional two-dimensional echocardiographic examinations. Still frames at end-diastole from apical four-chamber view were digitized and converted in matrices of 256 x 256 pixels. First-order statistical analysis was performed to describe a region of interest in the interventricular septum. The following parameters were studied: mean (gray level amplitude), standard deviation (overall contrast), uniformity (tonal organization), and entropy (tendency of gray levels to be spread). Myocardial structure was assessed in 75 of 78 subjects, divided into three groups: I, age 23-40 years; II, age 41-65 years; and III, > 65 years. Significant differences for all the parameters were found between the age groups. Age correlated directly with mean and entropy (r = 0.77 and 0.69, respectively) and inversely with uniformity (r = 0.70). Our results suggest that quantitative echocardiography can reveal age-related changes in myocardial structure that are characterized by a greater echogenicity and loss in tonal organization, possibly due to increased collagen content within the fibers.