Reactive oxygen species (ROS) are known to be involved in the pathophysiology of complex regional pain syndrome type I (CRPS I). Since the mitochondrial respiratory chain is a major source of ROS, we hypothesized that mitochondria play a role in the pathophysiology of CRPS I. The hypothesis was tested by studying mitochondrial energy metabolism in muscle tissue from amputated limbs of CRPS I patients. We observed that mitochondria obtained from CRPS I muscle tissue displayed reduced mitochondrial ATP production and substrate oxidation rates in comparison to control muscle tissue. Moreover, we observed reactive oxygen species evoked damage to mitochondrial proteins and reduced MnSOD levels. It remains to be established if the mitochondrial dysfunction that is apparent at the end-stage of CRPS I is also present in earlier stages of the disease, or are secondary to CRPS I. The observation of a reduced mitochondrial energy production combined with reactive oxygen species induced damage in muscle tissue from CRPS I patients warrants further studies into the involvement of mitochondrial dysfunctioning in the pathophysiology of CRPS I.