The objective of this chapter is to describe complex regional pain syndrome. Complex regional pain syndrome (CRPS) is a chronic pain disorder defined by the presence of distinct clinical features including allodynia, hyperalgesia, trophic changes and sudomotor and vasomotor abnormalities. CRPS occurs as a result of varying degrees or types of injury, where the pain experienced is characteristically disproportionate to the expected magnitude of pain from the tissue trauma. The etiology is multifactorial, but involves pain dysregulation with contributions from both the sympathetic nervous system and the central nervous system. The diagnosis of CRPS is largely a clinical diagnosis and one of exclusion. A reasonable differential diagnosis might be large or small fiber sensorimotor neuropathies, cellulitis, erythromelalgia, vasculitis, vascular insufficiency, lymphedema, deep vein thrombosis, and Reynaud’s phenomenon. Treatment of CRPS involves a multidisciplinary and multimodal strategy with a rehabilitation program at the forefront. A detail discussion on Treatment of CRPS has been also provided in this chapter.