OBJECTIVE Emerging evidences indicate that heat-shock protein 90 (HSP90) is associated with atherogenesis. However, the effect of HSP90 on plaque stability is largely unknown. In this study, we explored the role of HSP90 in plaque development and its regulatory mechanisms on vasculature. METHODS Heat-shock protein90-overexpression lentivirus (Lenti-HSP90) was used to transfect apoE-/- mice after constrictive collars were planted at the right common carotid arteries. RESULTS As a result, HSP90 gene overexpression led to reduction in en face plaque area and increase in unstable plaque with heavier accumulation of lipids. Concomitantly, more macrophages, less smooth muscle cells, and collagen were generated, suggesting aggravated inflammation. However, inhibition of HSP90 with 17-AAG, a HSP90-inhibitor, induced opposing effects. Moreover, HSP90 upregulated plaque MMP-8, which might be the underlying mechanism of the change in plaque vulnerability index. Further, the translocation of NF-κB was promoted by HSP90, while inhibition of NF-κB significantly reduced MMP-8 production, which is upregulated by HSP90. CONCLUSIONS These findings suggested that HSP90 governs plaque development and vulnerability, as well as inflammation, at least in part via MMP-8 and NF-κB signaling pathways.