The paper is concerned with original data on decoding the involvement of disorders of the lipoprotein metabolism and circulating immune complexes in the mechanism of damage to the vascular wall in diabetes mellitus patients. In addition to raised LDL and VLDL levels, activation of lipid peroxidation in erythrocyte membranes as well as change of the spectrum of fatty acids were revealed. Two types of immune complexes were formed in diabetes mellitus patients: insulin--antiinsulin antibodies and insulin--VLDL. Under certain conditions each of these complexes can produce a vasodamaging effect. In the author's opinion, the existence of such complexes determines the specific nature of microangiopathies in diabetes mellitus patients.