The activity of cholesteryl ester transfer protein (CETP) was assayed in sera of children and adolescents on continuous ambulatory peritoneal dialysis (CAPD) by coincubating lipoprotein-deficient samples with exogenous donor and acceptor lipoproteins. Serum levels of triglycerides, total cholesterol, low-density lipoprotein cholesterol and apolipoprotein B and apoliproprotein B/ apolipoprotein Al ratio were increased, while the high-density lipoprotein cholesterol level was decreased. The CETP activity in children on CAPD exceeded that in either adults or control children, and was correlated with low-density lipoprotein cholesterol, apolipoprotein B, and total cholesterol/ high-density lipoprotein cholesterol, low-density lipoprotein cholesterol/high-density lipoprotein cholesterol, and apolipoprotein B/apolipoprotein At ratios. The CETP activity in CAPD patients may be due to increased synthesis in response to a protein loss in the dialysis fluid and map exacerbate atherosclerosis.