The psychological response to detention is examined. It is argued that detention imposes severe stress and that many detainees seem to exhibit the characteristic symptoms of a post-traumatic stress disorder. The contention that detention is stressful is based on the fact that detainees are held in isolation and have no control over the situation, both of these factors having been shown to be associated with the experiencing of stress. Individual differences affecting the responses to stress are discussed, as are the long-term consequences of detention.