Background. In cases of severe trauma, fractures of long bones are the most often combined with trauma of the chest, head, and abdomen, as well as development of hemorrhagic shock. Therefore, it is reasonable to study the combined trauma of the chest and lower extremities in details, as well as the post-traumatic multiple organ dysfunction especially in early manifestation stage. Objective. The aim of the study was to identify the features of structural organization of the lungs, heart and liver with underlying combined trauma of the chest and both thighs on the 7th day of the post-traumatic period. Methods. The experimental study involved 22 adult nonlinear white male rats with body mass of 200-210 g, kept on a standard diet at animal facility with food and drinking regimes recommended by the standards for laboratory animals. All animals were divided into 2 groups: the control group (1st, n=10), the experimental group (the 2nd) chest trauma and both thighs trauma, observation for 7 days (n=12). The animals of the experimental group were simulated for right-sided closed pneumothorax with a rib fracture by a trocar under thiopental-sodium anesthesia (40 mg/kg of body weight of the rat, intraperitoneally); it was combined with a fracture of the left and right femurs. Skeletal injury was modeled on each thigh that caused a closed fracture by a single dosed blow with a specially designed device. The blow energy was 0.375 J that corresponds to a severe injury. The associated injury was simulated by successive infliction of both injuries. Results. Examination of the liver of animals on the 7th day of the experiment revealed a rapid growth of lesions in their parenchyma. The central veins were poorly visible and contained single erythrocytes; the vessels of medium caliber of myocardial stroma were dilated and blood-filled, which was manifested by the development of perivascular oedema. In the lungs of experimental animals, a moderate decrease of interstitial tissue oedema of the interalveolar septa was present, while cellular infiltration of mast cells, macrophages and lymphocytes also decreased significantly. Conclusions. Multiple organ injuries, which are characterized by structural changes in the liver, heart and lungs in the combined trauma of the thorax and thighs on the 7th day of experiment were evidenced.