In this work we investigated the influence of hyperlipemia on the fibrinolytic system and also attempted to determine whether vascular lesions may modify the response of plasminogen activators to hyperlipemia. The study was made on rats. Three different diets were administered to the animals, two of the diets only increased the levels of plasmatic lipids in the animals (hyperlipemic groups), but the third induced hyperlipemia and lipid infiltration in aorta (arteriosclerotic group). Fibrinolytic activity was evaluated in the plasma, on the aorta endothelial surface and in aorta wall. In the plasma, plasminogen activator (PA) activity was increased in the hyperlipemic and arteriosclerotic groups compared to control group, however, the activity of fibrinolysis inhibitors was also increased. On the endothelial surface and in the aorta wall, fibrinolytic activity was increased in the groups which received hyperlipidic diets but in the arteriosclerotic group only the endothelial surface showed a clear increase of fibrinolytic activity. A positive correlation was observed between PA activity and levels of hyperlipemia. However, no correlation has been shown between fibrinolytic activity in the aorta with cholesterol and triglyceride levels in this vascular wall.