Complex regional pain syndrome (CRPS) often causes serious impairments in activities of daily living and the ability to function. It can lead to a tremendous burden to patients and their families. There continues to be clinical confusion and misunderstanding about the syndrome due to its dramatic nature, limited knowledge of its mechanisms, and frequent lack of response to interventions. Research into CRPS has grown although our understanding remains incomplete. We will summarize our knowledge about CRPS, including epidemiology, pathophysiology, diagnosis, natural course, treatment, and prevention.