The relation between hemispheric lateralisation of intracerebral lesion and duration of impaired consciousness was investigated in 43 survivors of severe closed head injury. Duration of impaired consciousness, defined as the time from injury until the obeying of commands, was significantly longer in patients with left hemisphere than right hemisphere lesions. However, the side of intracerebral lesion had no effect on duration of impaired consciousness defined as time from injury until localisation to pain. Use of verbal methods to assess level of consciousness may be responsible for the observation that lesions of the language dominant hemisphere produce greater disturbance of consciousness than similar insults to the right hemisphere.