Endothelial and vascular disorders with the coagulation disorders, altered blood flow and increased permeability, vasoconstriction in diabetic patients and animals were seen. The membrane structures of blood components were affected by the disorders of blood flow and increased blood viscosity. For that reason, the investigation of diabetic effects on changing of peripheral and integral protein structures' in erythrocyte membrane in diabetic cats were aimed in this study. Totally 20 cats which of 10 were diabetic and their ages varied between 1.5 and 10 years old brought to Department of Internal Medicine, Faculty of Veterinary Medicine, and Istanbul University were used. Haematologic parameters were determined by Sysmex KX 21 haematology analyser. Erythrocyte membrane proteins were determined by SDS-PAGE electrophoresis using a 10% gel and a discontinuous buffer system. When compared to controls, SDS-PAGE revealed that the band 5 corresponding to actin was weaker while band 4.5 corresponding to integral membrane proteins (glycophorin A, B and C) had disappeared in diabetic cats. It was also seen that band 4.9, which is composed of dematin (a protein with actin-bundling capacity), was lost. The findings were thought that diabetes mellitus degenerate the structural proteins of the cell and affect the blood flow.