Malondialdehyde (MDA) is likely to be one of the main metabolites produced by superoxide anion, and the serum MDA level is usually found to be higher in hemodialysis (HD) patients than in normal controls. On the other hand, it is well known that low density lipoprotein (LDL) modified in vivo is mainly metabolised in scavenger cells such as macrophages (Mφ) which have the potential to develop into foam cells. Furthermore, MDA rich LDL is one of the modified LDLs therefore, the present study was undertaken to clarify whether or not LDL from HD patients is MDA LDL, and whether or not metabolism of these LDL in Mφ accelerates the transformation into foam cells. In addition, we examined the effects of hemodialysis and anti-oxidants.The HD patients were given α-Tocopherol (TOC) at a dose of 600mg per day for two weeks with the aim of reducing MDA. The HD patients' and controls' LDL levels were determined by the method of Havel et al. The degradation of LDL was determined according to the method of Goldstein and Brown. MDA levels in LDL were significantly higher in HD patients than in controls. TOC-treatment slightly reduced LDL-MDA levels in HD patients. The degradation of LDL in HD patients was obviously accelerated, compared to that in controls, and after TOC-treatment it recovered to a level similar to that in controls. HD produced no effect on LDL-MDA levels or degradation.In conclusion, these findings suggest that LDL from HD patients was modified with MDA and that this degradation of LDL accelarates atherosclerosis.