The purpose of this study is to evaluate the effect of combination therapy with cilostazol and probucol on plaque volume and composition change in comparison with cilostazol alone by serial intravascular ultrasound and virtual histology.

Inclusion Criteria:

1. Patients treated with PCI with stent
2. Male or female over 20 years of age
3. Presence of at least one PCI target lesion(lesion length ≤26mm) with ≥50% diameter stenosis that can be covered with a single Endeavor Sprint stent(Medtronic)
4. Other PCI target lesions also should be treated with Endeavor Sprint stents
5. Presence of an intermediate non-PCI target lesion with luminal narrowing of ≥30% and ≤70% by visual estimation
6. Signed written informed consent to participate in the study

Exclusion Criteria:

1. Intermediate (non-PCI target) lesions that might provide difficulty for IVUS evaluation because of following reasons: heavy calcification (>90° Arc), tortuous vessel with sever angulation, total occlusion, or bifurcation lesions

2. Previous PCI in the last 6 months

3. Previous CABG

4. Patients with AMI undergoing primary PCI or rescue PCI after thrombolysis

5. Cardiogenic shock

6. Inability to take adequate anti-platelet therapy

7. Thrombocytopenia (platelet count <70 x 109/l)

8. Known hypersensitivity or contraindication to any of the following medications: Heparin, aspirin, clopidogrel, cilostazol, probucol, statin, contrast media*

   *Patients with documented sensitivity to contrast media which can be effectively pre-medicated with steroids and diphenhydramine [e.g. rash] may be enrolled. Those with true anaphylaxis to prior contrast media, however, should not be enrolled.

9. History of severe ventricular arrhythmia

10. Significant QTc prolongation (≥470 ms) on ECG

11. NYHA class III/IV heart failure or LV ejection fraction ≤35%

12. Familial hypercholesterolemia

13. Uncontrolled hypertriglyceridemia (>400 mg/dL)

14. Chronic renal failure with serum creatinine level ≥2mg/dL

15. Severe liver disease or transaminase level ≥3 times the upper limit of normal.

16. Pregnant or breastfeeding