The artery wall adapts to changes in wall tension and wall shear stress by means of enlargement and changes in both thickness and composition. The intima may participate in these changes, and these compensatory adaptive-reactive modifications continue in the presence of atherogenesis. Further understanding of the interaction of the evolving plaque with the artery wall and the associated effects of the physical forces associated with the circulation should provide new insights into the nature of plaque instability and into the outcome of direct interventions.