Aim: This study was undertaken to investigate the physicochemical properties of modified low density lipoprotein (LDL) in diabetes. Methods: LDL from 10 type 1 and 10 type 2 diabetic patients, as well as LDL from 10 non-diabetic subjects, was subdivided into bound and non-bound fractions by affinity chromatography on Ricinus communis agglutinin-agarose, and further characterized by sialic acid content, hydrated density, electrophoretic mobility, and the ability to induce cholesterol deposition in cultured cells. Results: The non-bound LDL fraction was similar to native LDL from healthy subjects, with respect to its physicochemical properties, and did not produce intracellular cholesterol accumulation. The bound LDL fraction was characterized by several alterations differentiating it from... non-bound LDL, namely, significantly lowered sialic acid content (by 35-50%, compared with non-bound LDL), increased electrophoretic mobility (by 40-50%), increased hydrated density (difference in modae, 5.6-5.9 mg/mL), and smaller particle size (difference in modae, 3.8-4.9 nm). Bound LDL possessed the ability to induce a 2.1- to 2.7-fold increase in intracellular cholesterol content. Conclusion: The results showed the presence of a dense, small, more electronegative, desialylated LDL subfraction in the blood of diabetic patients, which is in vivo modified atherogenic LDL.