The authors have shown that in the medullary, intestinal and cerebral forms of acute radiation disease pathological changes of the lymphatic microvessels manifested themselves in the form of lymphostasis at the climax of disease in the medullary form of acute radiation disease and at the climax and in the terminal period in the intestinal form. A characteristic feature of the lymphatic channel involvement in the medullary form of acute radiation disease was a large number of erythrocytes in the lumen of the lymphatic vessels at the climax of disease. No changes of the mesenteric lymphatic channel of the rats were noted in the cerebral form. On the other hand, the presence of a large number of newly formed capillaries in the young rats at the climax of disease indicate the persistence of the proliferative ability of the lymphatic microvessel endothelium and its significant radioresistance.