Hemodynamic determinants of vascular changes in hypertension and atherosclerosis. Several new concepts are reviewed concerning structural and functional changes in atherosclerotic and hypertensive blood vessels. First, in regard to modulation of vascular changes, atherosclerosis appears to progress more slowly during hypotension than during normotension. This finding may have implications for the optimal level of blood pressure. Second, structural "remodeling" of the vessel wall occurs in both atherosclerosis and hypertension. Remodeling helps to preserve the arterial lumen despite intimal proliferation in atherosclerosis. In contrast, remodeling (which differs from vascular hypertrophy) reduces the vascular lumen in chronic hypertension. Third, functional changes impair active vasodilator responses in both atherosclerotic and hypertensive vessels, in part by endothelium-dependent mechanisms. Finally, we propose that leukocytes as well as platelets may be important cellular mediators of spasm in atherosclerotic arteries. 