[P.M.].Dyslipidemias are major risk factors for atherosclerosis and cardiovascular disease. Abnormalities of fibrinolytic and coagulation components are considered useful predictors of cardiovascular morbidity and mortality in adults. This study examined whether fibrinolytic and coagulation components are abnormal in children with dyslipidemia. Thirty-six children with asymptomatic dyslipidemia, and 26 control subjects underwent venous occlusion stress testing with collection of preocclusion and postocclusion blood samples. All samples were assayed for tissue plasminogen activator, plasminogen, plasminogen activator inhibitor-1, ␣ 2 -antiplasmin, ␣ 2 -macroglobulin, D-dimer, fibrinogen, and von Willebrand factor. Children with dyslipidemia had significantly decreased levels of tissue plasminogen activator in both preocclusion and postocclusion samples compared with control subjects, reflecting decreased fibrinolytic activity. Children with dyslipidemia also had significantly increased levels of plasminogen, ␣ 2 -macroglobulin, and fibrinogen in preocclusion and postocclusion samples compared with control subjects. In conclusion, decreased fibrinolytic activity is present in asymptomatic children with dyslipidemias, potentially reflecting endothelial dysfunction and increased risk of cardiovascular disease in early adult life. Further studies are required to determine the usefulness of this marker in predicting disease progression or response to therapy. (Pediatr Res 55: 576-580, 2004) Abbreviations DL, dyslipidemia tPA, tissue plasminogen activator PAI, plasminogen activator inhibitor vWF, von Willebrand factor VO, venous occlusion ␣ 2 -AP, ␣ 2 -antiplasmin ␣ 2 -M, ␣ 2 -macroglobulin CI, confidence interval TC, total cholesterol DL defines abnormalities in the lipid profile caused by both genetic and acquired metabolic disorders. Most of the genetic lipid disorders are dominantly inherited and include familial hypercholesterolemia, familial combined hyperlipidemia, familial hypertriglyceridemia, and familial hypoalphalipoproteinemia (1). Acquired abnormalities in lipid metabolism are most commonly related to obesity (2). Persistent abnormalities of the lipid profile during childhood are associated with accelerated atherosclerosis and increased cardiovascular risk in early adult life (3).Atherosclerosis is a chronic inflammatory response of the endothelium to metabolic and physical injuries leading to gradual accumulation of plaque in the vessel wall (4). The pathogenesis of atherosclerosis begins during childhood with the appearance of intimal lesions in the aorta of young children and fatty streaks in coronary arteries of adolescents. These lesions occur at the same vascular sites of atherosclerotic plaques observed in older ages (5-7). The process of atherogenesis leads to abnormal endothelial cell function that can be detected in the early stages, before anatomic evidence of plaque formation occurs (4,8).Studies in asymptomatic adults at risk for future myocardial infarction suggest that increased baseline p...