Management of patients presenting with traumatic persistent vegetative state (PVS) calls for extensive resources. The ability to predict whether or not a patient is likely to recover is a critical issue. In 12 patients with PVS admitted consecutively for early rehabilitation after head injury, pattern of brain activity was measured by 99mTc-hexamethyl-propylenamineoxime (99mTc-HM-PAO) brain SPECT (single photon emission computer tomography). All patients were re-investigated after a mean observation period of 3 years. A global reduction of cortical blood flow was a reliable predictor of poor long-term outcome, but the demonstration of only focal deficits did not reliably indicate a favourable outcome. Brain SPECT may help to improve outcome prediction in patients with traumatic PVS.