Cardiovascular disease is the leading cause of illness and death in the United States. Disorders of lipid and lipoprotein metabolism (dyslipidemia) predispose patients to premature atherosclerosis. Dyslipidemias can be classified as hypercholesterolemia, hypertriglyceridemia, combined hyperlipidemia, and low levels of high-density lipoprotein cholesterol. Elevated cholesterol levels can cause premature atherosclerosis, and high triglyceride levels can result in pancreatitis. The laboratory investigations that are useful in the diagnosis and management of dyslipidemia include measurement of cholesterol, triglycerides, high-density lipoprotein cholesterol, and low-density lipoprotein cholesterol, both directly and through calculation. Useful tests that can be done in the laboratory to exclude secondary causes of dyslipidemia are measurement of thyroid-stimulating hormone, blood glucose, liver enzymes, creatinine, and plasma and urine protein.