Tonic dystonia is an underrecognized complication of reflex sympathetic dystrophy syndrome (RSDS) characterized by an increase in muscle tone at the site of injury. Case-reports.- We describe five cases of tonic dystonia complicating RSDS of the lower extremity. There were four women and one man, with a mean age of 52 years. In addition to the typical features of RSDS, the patients had fixed equinovarus of the foot with hyperextension or hyperflexion of the great toe. In two patients, examination after spinal anesthesia showed that the deformity was reducible. Spontaneous resolution of the dystonia occurred in one patient. Another patient failed to experience meaningful improvement after a motor block followed by botulinic toxin injections. In two patients, the same treatment was followed by a slight improvement. Treatment options are still being evaluated in the last patient. Discussion.- Tonic dystonia is an underrecognized complication of RSDS that often develops after a minor injury yet causes prolonged pain and disability. Spread of the dystonia to other sites is not infrequent. The underlying mechanisms remain unclear but may involve dysfunction of the central or peripheral nervous system or psychogenic factors. Suggested treatments include motor block, intrathecal baclofen, sympathetic block, and sympathectomy. However, none of these treatments has been proved effective. Conclusion.- The five cases described here provide useful information on RSDS-associated tonic dystonia, a condition that runs a protracted course and remains difficult to manage.