A proliferation of cells, with characteristics of medial smooth muscle cells, occurs in the intimal region of the artery wall and has been considered important in the early phases of atherosclerosis (1,2). In addition, it has been claimed that cells on the surface of advanced lesions appear to be of monoclonal origin and different from the same cells in the media of adjacent normal tissue (3). These observations suggest that some form of alteration or transformation of the medial smooth muscle cell may occur in the atherosclerotic lesion.