This is a 12-week clinical trial in lipid clinic patients for whom niacin therapy is appropriate to evaluate the efficacy of MK0524 to improve the tolerability of extended-release niacin. There will be 6 scheduled clinic visits and 3 treatment arms.

Inclusion Criteria:

• Patient is appropriate candidate for niacin therapy
• Patients with evidence of ischemic cardiovascular disease must be on a statin and have LDL-C <130 mg/dL at V1
• Patients with diabetes mellitus and no evidence of ischemic cardiovascular disease must have LDL-C <130 mg/dL at V1
• Non-diabetic patients with 2 or more risk factors for coronary heart disease and no ischemic cardiovascular disease must have LDL-C <160 mg/dL at V1
• Patient has TG <500 mg/dL (5.65 mmol/L) at V1
• A patients historic serum or plasma lipid values measured within 6 months from Visit 1 may be used to meet lipid inclusion criteria
• ALL OTHER PATIENTS DO NOT REQUIRE SPECIFIC LIPID ENTRY CRITERIA

Exclusion Criteria:

• Patients with unstable doses of medications
• Pregnant or lactating women, or women intending to become pregnant are excluded
• Patients with diabetes mellitus that is poorly controlled, unstable or newly diagnosed
• Patients with: chronic heart failure, uncontrolled/unstable cardiac arrhythmias, unstable hypertension, active or chronic hepatobiliary disorder or hepatic disease, HIV positive, gout (within 1 year)