The purpose of the work was to study morphological changes in immunocompetent organs, liver and lungs during experimental endotoxemia induced by lipopolysaccharide (LPS). The histological method with hematoxylin-eosin staining and subsequent microscopic analysis was used in the work. The histostructural damage to the immune system organs (thymus, spleen, lymph nodes) occurs in experimental endotoxemia caused by LPS. There is a circulatory disorder with morphological changes in all layers of the vascular walls. Necrobiotic and necrotic damage to organ cells was also revealed. The liver of experimental animals underwent especially pronounced changes in histostructure. Significant microcirculation disorders with dilation and congestion of vessels of various sizes and significant damage to endothelial cells were identified. Necrotic changes in hepatocytes were accompanied by a significant increase in stellate reticuloendotheliocytes and increased lymphocytic infiltration, which is the basis for liver dysfunction and the development of an inflammatory immune reaction. In conclusion, the data obtained on the morphological manifestations of endotoxemic damage can serve as the basis for the development of effective therapeutic approaches in the treatment of LPS-induced internal organ damage.