The numerous components of the venoms of various animal species cause an extremely wide range of effects and symptoms in the recipient’s body. At the same time, the degree of severity of pathological changes is determined, in general, by the type of animal, the volume and method of toxin administration, as well as the characteristic features of the victim. Changes in the structural and functional parameters of the wall of the jejunum under the influence of viper venom are still poorly understood. Research aimed at identifying new components of snake toxins, determining the degree of their influence on the affected organism and using the obtained data for the production of antidotes, and thereby eliminating economic losses associated with snake bites, should be considered extremely relevant. The purpose of the study is to establish the manifestations of damage to the small intestine under the conditions of the action of the venom of the common European adder (Vipera berus berus). The experiment was conducted on 20 non-linear white male rats. During the study, rats were divided into two groups — control and experimental. Poisoning was modeled by intraperitoneal injection of common European adder venom at an ED50 dose of 1.576 μg/g to the rats of the research group. Histological preparations were examined under a SEO SСAN light microscope, images were processed using a Vision CCD Camera with an available image display system on a computer monitor. It was established that under the conditions of action of common European adder venom, the toxic substances of its venom cause destructive-degenerative changes in the relief and stromal-vascular components of the mucous membrane of the organ in the wall of the jejunum. Thus, increasing the permeability of the walls of vessels of the microcirculatory channel, thinning and complete destruction of the walls of hemocapillaries, together with the cytotoxic effect of the poison on erythrocytes, leads to the formation of multiple, small hemorrhages with hemolysis of erythrocytes.