Comparative morphological analysis of collagens I and III content in the connective tissue in various groups of surgical patients, including tumor patients with ventral hernias, was carried out. The total content of collagen and collagen I/III ratio were the highest in cancer patients in comparison with non-tumor patients with hernias and with patients without hernias or tumors. Hence, factors not associated with collagen synthesis predominate in the pathogenesis of hernia formation in patients operated for malignant tumors.