Background The Cutting Balloon (Interventional Technologies Inc) is a new-concept balloon that incorporates 3 to 4 blades to create sharp incisions on the luminal surface of the lesion during dilation without causing severe tearing injury to the vessel wall. It may reduce restenosis and improve clinical outcome. Methods Two hundred forty-eight lesions were randomly assigned to Cutting Balloon angioplasty (CBA, 120 lesions) or conventional balloon angioplasty (PTCA, 128 lesions). Inclusion criteria were type B/C lesions (American College of Cardiology/American Heart Association classification) and reference diameter <3.0 mm by visual image on angiogram. Quantitative coronary angiography was performed before and after percutaneous coronary angioplasty and at 3-month follow-up. The primary end point was restenosis, defined as ≥50% diameter stenosis at follow-up. Clinical event rates at 1 year were assessed. Results Baseline characteristics were similar. Reference diameter was small in both groups (2.16 vs 2.18 mm, CBA vs PTCA). Preprocedural percent diameter stenosis (%DS) was similar (69.8% vs 69.6%). However, postprocedural and follow-up %DS were lower (26.2% vs 28.9%, P = .072; 40.8% vs 47.5%, P = .011) in the CBA group. Restenosis was significantly lower (25.2% vs 41.5%, P = .009) in the CBA group. At 1 year, event-free survival was achieved in 72.8% of the CBA group and in 61.0% of the PTCA group (P = .047). Conclusion These findings suggest that CBA provides superior angiographic and clinical outcomes in comparison with PTCA in small coronary arteries. (Am Heart J 2001;142:782-9.)