Cholesterol deposition in the walls of blood vessels begins a complex pathological process called atherosclerosis. Atherosclerosis can eventually lead to blockage of the vessels usually by triggering a blood clot to form. When this process occurs in a coronary artery, the blockage can cause a heart attack. White blood cells (macrophages) respond to the buildup of vessel wall cholesterol. I will discuss mechanisms for cholesterol deposition in arteries and how macrophages function during development of atherosclerotic lesions.