During incubation of normal arterial tissue with serum lipoproteins, net transfer of cholesterol was observed in the direction from the lipoproteins into the arterial tissue. Such transfer was only observed during incubations with single, isolated lipoprotein fractions. It was independent of the type of lipoprotein, VLDL, LDL or HDL, which was incubated with the arterial tissue. On the other hand, no net transfer of cholesterol was observed during incubations of arterial tissue with a combination of serum lipoproteins equivalent to that in native serum. Studies on the transfer of radioactive cholesterol suggested that cholesterol elimination from arterial tissue in vitro was not affected by the composition of the incubation medium. Therefore, it is suggested that cholesterol accumulation more easily is influenced by the serum lipoprotein composition, and that serum lipoprotein dysbalance may promote cholesterol accumulation in the tissue. This effect may be present even when the dysbalance involves a decrease of specific serum lipoprotein fractions.