Ultrastructural evaluation was performed of the MK cytoplasm in the successive phases of experimental haemorrhagic shock in rats. Qualitative abnormalities were revealed in the intracytoplasmic structures of MK. Platelets in the circulating blood were evaluated. A correlation was found between the changes in the intracytoplasmic organelles and the number and biological activity of blood cells. The results obtained indicate significant disturbances in the functioning of the thrombopoietic system in experimental haemorrhagic shock, which are caused by alterations within the intracytoplasmic structures of MK and lead to platelet production from morphologically differentiated but functionally immature MK.