To evaluate the effect of atrovastatin therapy on borderline vulnerable lesions in patients with acute coronary syndrome (ACS) .Methods Patients with ACS underwent coronary angiography (CAG) and intravascular ultrasound (IVUS) investigation.Patients with culprit vulnerable borderline lesions were enrolled.No coronary inter-vention was performed on these lesions.All the patients received atrovastatin therapy for 12 months and underwent clin-ical follow-up along with IVUS follow-up.Cross section area (CSA) of the targeted lesion,CSA of the reference arter-ies (extra elastic membrane) ,minimal lumen CSA,and plaque area were measured at baseline and follow-ups.Ad-verse events included recurrent angina,recurrent myocardial infarction,revascularization and death.Results No ad-verse events was reported during follow-up period.Compared with baseline data,the level of ApoB decreased signifi-cantly at the end of the study (0.589 ± 0.136 g /L vs 0.681 ± 0.132 g /L,P = 0.03) .Both the percent diameter steno-sis and the percent area stenosis detected by CAG displayed minimal change ((62.50 ± 10.21) % vs (54.79 ± 12.35) % ,P = 0.48 and (58.61 ± 8.36) % vs (48.18 + 10.56) % ,P = 0.78) .Detected by IVUS,the minimal lu-minal CSA of the targeted lesion increased significantly (6.32 ± 2.42 mm2 vs 5.63 ± 2.51 mm2,P < 0.01) ,the plaque area and CSA stenosis decreased (7.70 ± 2.19 mm2 vs 8.17 ± 2.55 mm2,P < 0.05 and 56.94 ± 8.47% vs 61.4 ± 110.34% ,P < 0.01) .A total of 25 soft plaques (50% ) transformed into fibrous plaque.Conclusions Atro-vastatin therapy stabilizes borderline vulnerable plaque and reverses atherosclerosis progression in patients with ACS. To evaluate the effect of atrovastatin therapy on borderline vulnerable lesions in patients with acute coronary syndrome (ACS). Patients Patients with ACS underwent coronary angiography (CAG) and intravascular ultrasound (IVUS) investigation. Patients with culprit vulnerable borderline lesions were enrolled. No coronary inter -vention was performed on these lesions. All patients received atrovastatin therapy for 12 months and underwent clin-ical follow-up along with IVUS follow-up. Cross section area (CSA) of the targeted lesion, CSA of the reference arter- extra elastic membrane, minimal lumen CSA, and plaque area were measured at baseline and follow-up. Ad-verse events included recurrent angina, recurrent myocardial infarction, revascularization and death. Results No ad-verse events was reported during follow- up period. Compared with baseline data, the level of ApoB decreased signifi-cantly at the end of the study (0.589 ± 0.136 g / L vs. 0.681 ± 0.132 g / L, P = 0.03) .Both the percent di ameter steno-sis and the percent area stenosis detected by CAG displayed minimal change (62.50 ± 10.21)% vs (54.79 ± 12.35)%, P = 0.48 and (58.61 ± 8.36)% vs (48.18 + 10.56)%, P = 0.78) .Detected by IVUS, the minimal lu-minal CSA of the targeted lesion increased significantly (6.32 ± 2.42 mm2 vs 5.63 ± 2.51 mm2, P <0.01), the plaque area and CSA stenosis decreased (7.70 ± 2.19 mm2 vs 8.17 ± 2.55 mm2, P <0.05 and 56.94 ± 8.47% vs 61.4 ± 110.34%, P <0.01) .A total of 25 soft plaques (50%) transformed into fibrous plaque. Conclusions Atro- vastatin therapy stabilizes borderline vulnerable plaque and reverses atherosclerosis progression in patients with ACS.