A survey of self-injurious behaviour in people receiving services for mental handicap was carried out in one health region. Six hundred and sixteen adults and children were found to have engaged in self-injurious behaviour sufficient to have caused tissue damage in the previous 4 months and 596 of these were screened. Half were resident in hospital while 28% were in non-hospital residential care and the remainder (21%) were living at home. Nearly one-fifth (19%) showed self-injurious behaviour, of one or more types, at a rate of at least once per hour and a further 13% wore protective or restraining devices for all or part of the day or night. Only 2% were enrolled on formal psychological treatment programmes but nearly half were receiving psychotropic drugs (excluding anticonvulsants).