Environmental influences have been reported to play a role in the genesis of both schizophrenia and violent behaviour. We studied the central features of the family and social influences of 103 healthy non-offenders, 103 non-schizophrenic offenders, 103 schizophrenic non-offenders, and 103 schizophrenic offenders, using a semistructured instrument. Lower social class of origin, offending behaviour in the parental generation, loss of the father, a new partnership of the remaining parent, growing up in blended families, larger sibships and stays in foster homes during childhood and adolescence, promoted the development of offending behaviour in general. Schizophrenic patients were more likely to have relatives with schizophrenia, a finding which was more marked among offenders than non-offenders. We were able to identify characteristic unfavourable family and social influences which were associated in schizophrenic patients with a high risk of offending behaviour. This offers the prospect of early detection of those with schizophrenia who will go on to offend.