In the morphometric analysis, there was no pattern of hyperplasia among the groups because some animals had hyperplasia of the muscle layer with breakdown of muscle cells and calcium deposition; others only had a change of intima such as stratification of the intimal layer and muscle invasion; and others showed change in two layers, suggesting that there are various mechanisms underlying the development of myointimal hyperplasia, even though there were only two induction mechanisms — the hypercholesterolemic diet and endothelial injury (balloon). However, these findings are in contrast with those from the literature, which states that the distribution of hyperplasia may be intimal, diffuse, focal, or within the body vessel. Furthermore, Van Craeyveld et al. found that the main changes of atherosclerosis and hyperplasia actually occur in the deep layers of the vessel (muscle) and not in the intima. The staining method of Verhoeff, which is used for elastic fibers, was performed to try to define the intima and the muscle of vessel to calculate only the intimal hyperplasia; however, it was not effective in this delimitation. Therefore, we studied the myointimal layer.