Interleukin-8 (IL-8), also known as CXCL8, GCP-1, and NAP-1, is a widely expressed proinflammatory member of the CXC family of chemokines. This chemokine is secreted by a variety of cell types including monocyte/macrophages, T cells, neutrophils, fibroblasts, endothelial cells, and various tumor cell lines in response to inflammatory stimuli (IL1, TNF, LPS, etc). IL-8/CXCL8 can associate into a homodimer or a heterodimer with CXCL4/PF4 (2), and it can interact with matrix and cell surface glycosaminoglycans. Near its N-terminus, this 8-9 kDa chemokine contains an ELR motif which is important for its angiogenic properties. Numerous observations have established IL-8/CXCL8 as a key mediator in neutrophil-mediated acute inflammation due to its potent actions on neutrophils. In addition, IL-8/CXCL8 has crucial roles in various pathological conditions such as chronic inflammation and cancer. It induces VEGF expression, vascular endothelial cell proliferation, angiogenesis, and tumor cell invasiveness.