The objective of the study is to find peculiarities of the anoderm structural changes of morphogenesis in patients with chronic anal fissures (CAF) for further substantiation of therapeutic methods. The material of the study was the tissues of dissected anal complex (bottom and margins of ulcer, hypertrophic anal papilla, sentinel pile) from 33 patients. Histological examination found the defect of the stratified squamous epithelium. The epidermis of the marginal area of the wound, hypertrophic with signs of parakeratosis and acanthosis, hanged over the bottom. The surface of the bottom and margins of the wound in 31 cases (94%) was with thickening of rough fibrous masses. The bottom of ulcer in 29 (88%) cases is presented by sclerosed connective tissue. An increased amount of collagen fibers was found forming fuchsinophil is bundles. In 24 (73%) cases the scar on the fuchsine bottom of fissure was 3,4 mm (0,3±0,02) in deep. There are separate complexes of newly formed blood vessels with prevailing localization in the lateral walls of the wound. The blood vessels were with main by fibrosis in deep areas of the wound. Moderate interstitial edema and focal interstitial inflammatory infiltration mostly of lymphocytes and fibroblasts were detected; the amount of macrophages was not substantial. Considering cicatrical rebuilding of the anoderm of ulcer bottom caused, first of all, by hypoxia leading to activation of collagen-producing function of fibroblastes and absence of the signs of epithelization, patients with CAF should be treated surgically dissecting the bottom and margins of fissure in the complex with hypertrophic anal papilla and sentinel pile.