The role of the lipid-rich core region in atherogenesis is beginning to be understood, from its inception in early lesions to its catastrophic effects in promoting plaque rupture in late lesions. Besides the lipid-rich core, recent studies on human and animal atherosclerosis have drawn attention to atherogenic lipoproteins larger than LDL, unesterified cholesterol in lesions, apolipoprotein E as an antiatherogenic factor, macrophages as atherogenic effector cells, and unexpectedly slow rates of smooth muscle cell proliferation.