A study is reported of a controlled trial of social intervention in the families of schizophrenic patients at high risk of relapse. The patients were selected for being in high contact with high Expressed Emotion relatives. All patients were maintained on neuroleptic drugs. One half of the 24 families were randomly assigned to routine out-patient care, while the other half received a package of social interventions. This comprised a programme of education about schizophrenia, a group for the relatives, and family sessions for relatives and patients. The relapse rate in the control group was 50 per cent compared with nine per cent in the experimental group (P = 0.04). The stated aims of the therapeutic interventions were achieved in 73 per cent of experimental families. In these families, no patient relapsed. The results provide evidence for the causal role of relatives' expressed emotion (EE) in schizophrenic relapse, as well as for the therapeutic effectiveness of social intervention combined with drug treatment.