Heme oxygenase-1 (HO-1), an inducible heme-degrading enzyme, is expressed by macrophages and endothelial cells in response to various stresses and mediators of inflammation. HO-1 has been recently implicated in regulation of angiogenesis via expression of VEGF. The purpose of this study was to determine the effects of HO-1 modulation on the collagen-induced arthritis (CIA) model and on angiogenesis via up- regulation of VEGF expression in human synovial fibroblast. DBA/1J mice were treated with an inhibitor of HO-1, tin protoporphyrin IX (SnPP), or with an inducer of HO-1, cobalt protoporphyrin IX (CoPP), from day 1 to day 35 after CIA induction. The clinical evolution of disease was monitored visually. At the end of the experiment, histopathologic changes were examined on the joints. VEGF expression in paws were measured by immunohistochemical stain. mRNA expression of HO-1 and VEGF stimulated with various concentration of $TNF-{alpha}$, CoPP accessed on human synovial fibroblast by RT-PCR. Effects of pretreatment with SnPP on mRNA expression of HO-1 and VEGF in the presence of CoPP and $TNF-{alpha}$ in synovial fibroblast was accessed by Real-time RT-PCR. Administration of cobalt protoporphyrin IX significantly induced the inflammatory response, with increased arthritis index and expression of VEGF in the paws of the arthritis models. Treatment with SnPP significantly reduced the severity of CIA through inhibition of joint inflammation and cartilage destruction. The expression of VEGF were also significantly reduced by SnPP treatment in the paw. CoPPIX as inducer of HO-1, increased HO-1 and VEGF expression dose dependently in synovial fibroblast. In contrast, inhibition of HO-1 activity by SnPPIX abrogated CoPPIX-induced HO-1 and VEGF production in synovial fibroblast. Stimulation with $TNF-{alpha}$ increased HO-1 and VEGF expression itself and showed additive effect on HO-1 and VEGF expression when it treated with CoPP. When SnPP was treated with CoPP and $TNF-{alpha}$, it abrogated the CoPP induced HO-1 and VEGF expression and also abrogated $TNF-{alpha}$ induced HO-1 and VEGF expression in synovial fibroblast. The effects of HO-1 induction in rheumatoid arthritis results in aggravation of arthritis via up-regulation of VEGF. I concluded that inhibition of the expression or activity of HO-1 could be a therapeutic target of rheumatoid arthritis.