The objective of the study was to examine and evaluate morphometrically age-related changes in the structure of myocardium collagen network of auricle of the right atrium in control group persons, who were not diagnosed with cardiac pathology leading to heart lesion or overload, and in ischemic heart disease patients. Material of 56 persons of both genders aged 20-94 years was used for study purposes. Biopsy material of 17 healthy persons (control group, average age 60.53+/-9.89 years) and autopsy material of 39 ischemic heart disease patients (average age 63.83+/-15.67 years) taken from the basis of auricle of the right atrium (specimen size--2 mm x 2 mm) were examined. Morphometric analysis of collagen network was performed using histologic and video morphometric methods. After this investigation we evaluated quantitative parameters of the bundles of collagen net--namely area, number, perimeter. The percentile occupied area of bundles in control group was 17.6+/-2.5%; ischemic heart disease patients group--26.8+/-2.9%; number of bundles was 4179+/-1073 and 2523+/-867; perimeter--24163+/-3308 mm and 23426+/-409 mm, respectively. After investigation of age-related changes of collagen network in control group and ischemic heart disease patients' group, which did not statistically significantly differed by age, we determined that collagen network area in auricle of the right atrium increased with age in both groups, however, spatial distribution of collagen network was different. Collagen network area enlarged with lengthening of its fibers along cardiomyocytes in control group. In ischemic heart disease group, it enlarged both in parallel to cardiomyocytes and by separate collagen fibers merging into bigger bundles. Fibrillar collagen network area and its total perimeter of healthy persons increased with age, and number of fibers did not change. Consequently, collagen fiber area of one location increased with age; its shape, judging by in parallel increasing total perimeter, became branchier, i.e. proliferated in endomysium in parallel with cardiomyocytes. In ischemic heart disease group fibrillar collagen network percentage area increased with age, however, total perimeter and number of separate fibers in visual field decreased. Consequently, in ischemic heart disease group separate collagen fibers merged, their locations enlarged, taking an integral structure, which allowed assuming development of interstitial fibrosis.