One shot treatment of rabbits with epinephrine or atherogenic substance induced an acute infiltration of γ-globulin, fibrinogen, and β- lipoprotein into the arterial wall with subendothelial stagnation, temporarily dammed by the internal elastic lamina. Gamma-globulin, fibrinogen, and β-lipoprotein are also visualized in chronic experimental atheromata. This model utilizes a physiological marker to study vascular permeability and suggests an important barrier function of the internal elastic lamina.