This paper reviews the research investigating the vegetative state (VS) in terms of its aetiology and prognostic factors that may be indicative of the outcome for patients in the VS. The VS is a relatively rare syndrome that still causes confusion for treating clinicians. In short, the VS is a clinical condition of unawareness of self and environment but with retained wakefulness. Until relatively recently there were no universally accepted diagnostic criteria, which caused problems both in terms of diagnosing the patient and in determining the incidence of the VS. This paper examines the most relevant and up to date work in order to determine if there is a way of predicting whether the VS for any given patient will be persistent (i.e. recovery is still possible) or if it is permanent and further treatment is futile. Currently, the most accurately available method to predict the prognosis of a patient in the VS is through clinical assessment of the patient combined with knowledge of the aetiology and duration of the VS. More work is needed in order to allow for the prediction of the outcome of the VS with greater certainty.