Objectives: in patients with familial hypercholesterolemia (FH), the propensity towards atherosclerosis may vary considerably. In the general population, a positive family history is associated with an increased risk for cardiovascular events. Since endothelial dysfunction is predictive for future cardiovascular events, we evaluated whether FH-children with a positive family history of premature cardiovascular disease have more pronounced endothelial dysfunction compared to children with a negative family history. Study design: 50 FH children, 10-18 years, participated in this study. Thirty-one children had a positive family history for cardiovascular events (fh + ) and 19 children had no events in the family (fh - ). Nineteen matched siblings participated as controls. Endothelial function was assessed by testing the flow mediated dilatation (FMD) of the brachial artery. Results: baseline characteristics were comparable for fh + , fh - and controls. Lipid levels were significantly higher in FH children. In FH, FMD was impaired compared to controls (11.7+/-4.4 vs. 15.6+/-6.8%, P<0.03). In addition, FMD was significantly lower in fh + compared to fh - (10.7+/-9.9 vs. 13.3+/-4.6%, P<0.05). Conclusion: In FH-children, endothelial function is impaired compared to matched controls. This impairment is most pronounced in FH children with a positive family history of premature cardiovascular disease.