The pre-morbid characteristics of 32 children requiring inpatient rehabilitation following moderate or severe head injuries were studied prospectively. Teachers completed Rutter and modified Conners questionnaires on the pre-head injury behavioural characteristics of each child and also rated the pre-morbid learning ability of the children on a four-point scale. The children's socioeconomic status was determined using their postcode at the time of the injury. Behavioural questionnaires were returned for 25 of the 32 children. Five of the 25 children obtained total behaviour problem scores on the Rutter teacher scales indicative of pre-morbid psychopathology. The general learning ability of five children was rated as being far below average. The children had a higher mean socioeconomic deprivation score than for the geographic area in which the rehabilitation unit is sited. The incidence of pre-morbid behaviour problems in the study population with moderate or severe traumatic brain injury may be somewhat higher than in the local population, but this did not appear to be a major risk factor in sustaining a head injury. However, adverse environmental conditions, linked to socioeconomic deprivation, did appear to be important risk factors that contributed to a pedestrian road traffic accident.