OBJECTIVE To determine the effects of meningitis in infancy on subsequent teenage behaviour. METHODS A national postal survey of parents and teachers using an established standard behavioural questionnaire. Subjects were 739 of the surviving children from the national incidence study of infantile meningitis in England and Wales carried out between 1985 and 1987, together with a group of 606 matched controls that had been recruited when the index cases were 5 years old. RESULTS 46% of parents of children who had had meningitis with complications in infancy, compared with 21% of parents of control children rated their children as having behavioural problems. When the children were rated by their teachers, 37% and 23% respectively, were scored as having behavioural problems. There was no significant difference in behaviour between the 103 children who had had meningitis during the first month of life and the 634 who had had postneonatal meningitis. Eight of the index children had been excluded from school compared to none from the control group. CONCLUSIONS The behaviour of teenage children who had meningitis in infancy is worse than that of control children who did not have infantile meningitis when rated by parents and teachers.