Objective: To summarize and analyze the mechanism, classification and treatment of complex regional pain syndrome in order to further the study of its nature. Data sources: The relevant articles to complex regional pain syndrome published in English between January 1980 and June 2005 were searched in Medline database with computer by using the keywords of "complex regional pain syndrome, reflex sympathetic dystrophy, casualgia". Study selection: Over 160 articles were selected firstly. Inclusive criteria: definition, classification, mechanism and treatment related to complex regional pain syndrome. Exclusive criteria: repetitive studies. Data extraction: There were 53 literatures in accordance with the crite ria, and 29 were selected for analysis. Data synthesis: Complex regional pain syndrome is one of pain diseases without clear mechanisms and effective treatments. Multiple factors play a role in the generation and maintenance of complex regional pain syndrome. It can be classified into two types: complex regional pain syndrome I and complex regional pain syndrome II based on the relation to sympathetic nervous system function and definable nerve lesion. The characteristics of its clinical presentation include excruciating pain and hyperaesthesia, autonomic nerve disorders, motor dysfunction and dystrophy, etc. Rehabilitation, pain management and psychological therapy are the mainstay of treatments for complex regional pain syndrome. Conclusion: Complex regional pain syndrome has a complex etiology, and is very difficult to treat. Large numbers of clinical and experimental studies are needed to explore its mechanism, effective prophylactic and therapeutic methods.