Midbrain lesions were found in 23 of 35 autopsied, head-injured people. These lesions were interpreted as “primary” that is. occurring at the time of impact. This interpretation was concordant with the clinical data, although the difficulty in establishing the precise moment at which the lesions were initiated in any individual case was recognized. Correlative clinicopathological data in head-injured people showed that midbrain damage could be determined by evoked potentials (EPs). In a total of 165 head-injured patients, the early presence or absence of evidence for midbrain lesions on EP examination was a powerful prognostic indicator of death or recovery. respectively. Autopsy and HP data showed that midbrain damage almost always occurred in the presence of hemispheric injury, but this fact should not obscure either the high frequency of midbrain lesions in those dying of head injury or the great prognostic value of their presence or absence.