To define a vegetative state (VS) as permanent is to declare its irreversibility. In 1994 a North-American multidisciplinary task force, by extensively analysing the literature, concluded that the recovery of consciousness from a post-traumatic or non-traumatic VS is unlikely after 12 and 3 months respectively. These conclusions did not obtain unanimous consent. The term permanent was in fact inappropriately used to define either the loss of consciousness or of function. Furthermore, patients with traumatic brain injury have been shown to recover the consciousness in a substantial greater percentage (6-7%) than previously appreciated (1.6%). This is hardly compatible with the peremptoriness of the term permanent, which should be used only in case of certainty. Ancillary tests are important in defining the prognosis. Patients in deep coma after an anoxic brain injury can be predicted as having a poor prognosis (death or permanent VS) with 100% specificity within one week of the insult. Magnetic resonance of the brain can predict patients at high risk of permanent VS within 6-8 weeks of a traumatic brain injury. In conclusion, the available evidence does not permit to define with certainty the patients who have irremediably lost their consciousness after a devasting brain insult. However, it seems possible to reliably define the risk of severe disability. Whether or not this knowledge might or should be used to titrate the intensity of therapeutic approach is to be defined. In this respect, it is central the definition of what an "acceptable outcome" is, certainly not an exclusive medical attribution.