Dyslipidemias in patients with coronary heart disease confer a greater risk of ischemic cardiac events than comparable dyslipidemias in people free of disease. A major dyslipidemia can be diagnosed in more than 80% of patients with established premature coronary heart disease. These dyslipidemias constitute not only elevations of low-density lipoprotein cholesterol (hypercholesterolemia) but also indicate abnormalities in the metabolism of triglyceride-rich lipoproteins, high-density lipoproteins, and lipoprotein(a). Clinical trials have demonstrated that therapy to lower low-density lipoprotein levels can delay angiographic progression of coronary stenoses and reduce recurrent cardiac event rates. These clinical benefits from low-density lipoprotein cholesterol lowering may occur as early as 6 to 12 months after initiation of therapy. Intervention strategies for dyslipidemias are directed toward lowering the low-density lipoprotein cholesterol fraction to 90 to 100 mg/dl. This approach begins with dietary modification, weight loss, smoking cessation, and aerobic exercise. Patients with hypercholesterolemia refractory to nonpharmacologic intervention require lipid-lowering agents. The choice of lipid-lowering medications is influenced by concomitant abnormalities of lipoprotein metabolism, such as hypertriglyceridemia or hypoalphalipoproteinemia. Treatment of primary dyslipidemias other than hypercholesterolemia may be warranted in the presence of other cardiac risk factors; however, a broader spectrum of clinical trial data is needed to support or refute this contention.