Dyslipidemia accompanies end-stage renal disease (ESRD) and contributes to the high incidence of cardiovascular disease in patients on chronic dialysis treatment. The lipid abnormalities of elevated triglyceride level and reduced high-density lipoprotein cholesterol level that occur in ESRD are associated in the normal population with an altered distribution of low-density lipoprotein (LDL) particle size, a pattern associated with increased risk of coronary heart disease. To assess the effect of ESRD on LDL particle size distribution, we examined plasma lipid levels and LDL particle size in 43 subjects on chronic hemodialysis, 23 subjects on continuous ambulatory peritoneal dialysis, and 30 control subjects with normal renal function. Of subjects on continuous ambulatory peritoneal dialysis, 48% had small LDL particle size compared with 23% of subjects on hemodialysis and 7% of control subjects. Subjects on both forms of dialysis also had higher triglyceride levels and lower high-density lipoprotein cholesterol levels that correlated with LDL particle size. We conclude that altered LDL particle size forms an important component of the metabolic abnormalities that contribute to the increased cardiovascular risk found in ESRD.