The subcellular localization and translocation of signaling proteins have risen large interest in the study of cellular signal transduction. MAP kinase pathways are key signaling systems in eukaryotic cells. MAP kinases have relatively specific localization in cells, and translocate into nucleus upon appropriate stimuli, leading to consequent physiological effects. It has been shown that the phosphorylation state of MAPKs as well as the interactions between MAP kinases and other proteins such as the upstream kinases, phosphatases, and downstream substrates may play a role in their specific localization and translocation. The elucidation of the mechanisms of localization and translocation of MAP kinases will be helpful to understand their in vivo functions.