Complex regional pain syndrome (CRPS) is an old problem with a new name. In the past, type 1 was termed reflex sympathetic dystrophy (RSD) and type 2 was called causalgia. The first half of this course discusses the fundamentals of CRPS, its clinical manifestations and basic treatment. The second half discusses diagnostic testing, followed by treatment modalities with particular attention on ketamine infusion therapy. Interspersed will be case presentations and atypical signs and symptoms of CRPS.