Background and Objectives: The ubiquitin-proteasome system is the major intracellular protein degradation pathway in the eukaryotic cells. Bortezomib inhibits 26S proteasome-induced I-κBα degradation and suppresses nuclear factor-kappa B (NF-κB) activation. We ex-amined the effect of bortezomib on neointima formation after of a rat carotid artery balloon injury. Materials and Methods: After carotid artery balloon denudation, bortezomib was immediately administered by tail vein injection (sys-temic treatment) and by using an F-127 pluronic gel (perivascular treatment). Two weeks after the injury, we compared the degree of neo-intima formation in the carotid artery and the tissue expression patterns of NF-κB and I-κBα. Results: The systemic treatment group exhibited a 29% reduction in neointima volume at two weeks after the balloon injury. On the west-ern blot analysis, the bortezomib group exhibited an increased I-κBα expression, which suggested the inhibition of I-κBα degradation. On immunofluorescence analysis, the nuclear import of NF-κB was clearly decreased in the systemic bortezomib group. The perivascular bort-ezomib treatment group exhibited a significant reduction in the neointimal area (0.21 ±0.06 mm 2 vs. 0.06±0.01 mm 2 , p<0.05), the neointima/media area ratio (1.43±0.72 vs. 0.47±0.16, p<0.05) and the % area stenosis (45.5±0.72% vs. 14.5±0.05%, p<0.05) compared with the con-trol group. In situ vascular smooth muscle cell proliferation at 2 days after the injury was significantly inhibited (24.7 ±10.9% vs. 10.7±4.7%, p<0.05). Conclusion: Bortezomib suppressed NF-κB activation through the inhibition of I-κBα degradation, and significantly reduced neointima formation in a rat carotid artery injury model. These data suggested that bortezomib represented a new potent therapeutic agent for the prevention of restenosis.