The complex regional pain syndromes (CRPS I and CRPS II), also known as reflex sympathetic dystrophy and causalgia, have been recognized for the past 2,500 years. Despite its long history, the diagnosis and treatment of CRPS are still challenging. These syndromes can be characterized by discrete sensory, motor, and autonomic findings, but many patients with CRPS continue to suffer for years without the diagnosis. Although much progress has been made in the understanding of CRPS, many questions still remain unanswered. CRPS is probably a disease of the central nervous system. Yet, peripheral inflammatory processes, abnormal sympathetic-afferent coupling, and adrenoreceptor pathology may also be part of the picture. A close multidisciplinary approach amongst the pain medicine consultants, psychologist, physical and occupational therapists, and neurologist is necessary to achieve the maximum treatment outcomes. If conventional treatment (e.g. pharmacotherapy) fails to show a significant response within 12 weeks, an interventional technique such as spinal cord stimulation (SCS) needs to be tried. The current concepts of CRPS could be replaced by a new mechanism-based term or group of terms in the near future leading to improved clinical guidelines. This article reviews the different aspects of CRPS including its definition, classification, epidemiology and natural history, clinical presentation, pathophysiology and management.