The rationale of treatment to prevent or delay the onset of atherosclerotic disease is based upon recognition that a key process in atherogenesis is the uptake of certain lipoproteins by scavenger cells in the artery wall. These lipoproteins enter the artery wall from blood. Thus the risk of atherogenesis is linked to the concentrations of these lipoproteins in plasma. Although a number of processes involved in atherogenesis may ultimately yield to additional means of intervention, the current central strategy is to reduce levels of atherogenic lipoproteins in blood. This strategy draws support from several recent intervention trials, which have shown reduction of progression of coronary disease and, in one instance, reduced total mortality. Recent advances in therapy, including the advent of HMG CoA reductase inhibitors and the development of combined drug regimes of unprecedented effectiveness, now permit the reduction of plasma lipoprotein levels to the optimum in a majority of individuals. Rational selection of single-drug regimens and drug combinations is based on phenotypic characterization of lipoprotein disorders. The physician also needs to be aware of disease that can lead to secondary hyperlipoproteinemia so that the underlying disorders can be treated if possible. The treatment by diet of all individuals with hyperlipidemia or atherosclerotic disease is recommended. The decision to treat with drugs should involve consideration of risk factors such as the patient's sex, blood pressure, smoking habits, levels of HDL, and family history of atherosclerosis.