Objective. Interleukin-18 (IL-18) is a proinflammatory cytokine implicated in the pathogenesis of rheumatoid arthritis (RA). This study was undertaken to examine the role of IL-18 in up-regulating secretion of the angiogenic factors stromal cell-derived factor 1␣ (SDF-1␣)/CXCL12, monocyte chemoattractant protein 1 (MCP-1)/CCL2, and vascular endothelial growth factor (VEGF) in RA synovial tissue (ST) fibroblasts, and the underlying signaling mechanisms involved.Methods. We used enzyme-linked immunosorbent assays, Western blotting, and chemical inhibitors/ antisense oligodeoxynucleotides to signaling intermediates to assess the role of IL-18.Results.