Familial hyperlipidemia is a group of genetic disorders with a predisposition to atherosclerosis. Hyperlipidemia causes increased atherosclerotic events through increased endothelial damage. In this report we aimed to measure the plasma fibrinogen and von Willebrand factor antigen (VWf:Ag) levels in pediatric patients with familial hyperlipidemias and to investigate the effects of serum lipid levels and antihyperlipidemic agents on these parameters. Of the 41 patients analyzed, vWf:Ag level was significantly lower in antihyperlipidemic receivers (132+/-51%, 102+/-19%; p=0.010). This finding may indicate that early initiation of antihyperlipidemics in patients with familial hyperlipidemias may decrease the risk of future atherosclerotic events through not only decreasing the serum lipid levels, but also decreasing plasma vWf:Ag levels.