Two groups of patients will participate in this study: patients with complex regional pain syndrome type 1, or CRPS-I (also called reflex sympathetic dystrophy) and patients with complex regional pain syndrome type 2, or CRPS-II. CRPS-I is pain that develops after relatively minor injury to an arm or leg, but lasts much longer and is much more severe than would normally be expected. CRPS-II is pain resulting from injury to a large nerve. Candidates will have a history and physical examination, blood tests, and electrocardiogram. Participants will undergo the following tests and procedures: