Background: In-stent restenosis (ISR) still has been a clinical situation difficult to solve. There is no randomized trial to prove the efficacy of radioactive liquid balloon for the treatment of ISR. Therefore, we sought to investigate the effect of holmium-166 liquid balloon system. Methods: From March 2002 to August 2003, 72 ISR patients (60 짹 10 years [range, 26-78], 53 male) were randomly enrolled either brachytherapy or control group. Before brachytherapy, cutting balloon, sized equal or up to 0.5 mm greater size, were used. To avoid geographic miss, 5 mm longer balloon was used. Treated arteries included LAD in 45 patients (60%), RCA 20 (27%), LCx 7 (9%) and left intermedius branch 2 (4%). Inclusion criteria of lesion length was between 10 to 35 mm and vessel diameter of 2.6 to 4.0 mm. Exclusion criteria was creatinine level > 2.0 mg%, pregnancy and age greater than 80 years. Before and after the procedure, aspirin and clopidogrel (75mg/day) or ticlopidine (500mg/day) were taken in all patients for at least 1 year. Follow-up angiography is schedule on 8 months. Results: There were no In-hospital MACE and 30 days events. Conclusions: Mid-term result will be presented.