Abstract
This report is based upon a study of multiple segments of the cardiovascular system of 200 deceased persons and selected surgical specimens. Mast cells are present in the adventitia of all blood vessels. Only the largest vessels have mast cells in the intima and subintima as well. In this location the number of mast cells is highest in grossly normal but microscopically edematous areas. Mast cells are rarely present in early and are never present in advanced atheromatous lesions. The theory is advanced that mast cells are attracted by plasma insudate to release heparin for degradation of lipoproteins. Thus, mast cells might play a role in atherogenesis.