Mitogen-activated protein (MAP) kinases comprise a family of protein-serine/threonine kinases, which are highly conserved in protein structures from unicellular eukaryotic organisms to multicellular organisms, including mammals. These kinases, including ERKs, JNKs and p38s, are regulated by a phosphorelay cascade, with a prototype of three protein kinases that sequentially phosphorylate one another. MAPKs transduce extracellular signals into a variety of cellular processes, such as cell proliferation, survival, death, and differentiation. Consistent with their essential cellular functions, MAPKs have been shown to play critical roles in embryonic development, adult tissue homeostasis and various pathologies. In this review, we discuss recent findings that reveal the profound impact of these pathways on chronic inflammation and, particularly, inflammation-associated cancer development.