Atherosclerosis is the most frequent disease in the majority of cardiovascular arteries. It is a complex disease with peculiar characteristics, including its principal localisation in the inner stratum of the artery (the intima). The paper examines 36 atherosclerotic lesions in elderly patients in which the presence of stenosing atherosclerotic plaque had been diagnosed. The presence of replicating DNA was demonstrated using flow cytometry together with a proliferative phenomenon within the fibrous-atherosclerotic plaque due to an hypothesised migration of smooth muscle cells inside the intima, leading to the final result, a gradual restriction of the arterial gauge and consequent alteration to blood flow. The plaques examined were localised at the bifurcation of the carotid artery, an area in which it is easier to find the physical and biochemical factors facilitating platelet adhesion, which together with other cells produce mitogenic activity since they release growth factors and create the conditions for the proliferation of fibrous tissue.