Eleven consecutive patients fulfulling criteria for the reflex sympathetic dystrophy syndrome (RSDS) were studied by quantitative clinical methods, providing measurements of swelling (ring size), tenderness (dolorimeter) and functional capacity (grip strength). The predominantly affected extremity was clearly identified by these technics and its serial progress determined in six patients. Corticosteroid therapy predictably resulted in improvement of all treated patients. Greater tenderness was found in the joints than in the interjoint areas, indicating a possible accentuation of the disease process in juxta-articular tissues. Synovial biopsy specimens in four patients were abnormal, and the histology was presented in detail for the first time. All patients showed bilateral involvement during the study, providing evidence for a central neural mechanism in the RSDS.