The possible role of environmental stress in precipitating the onset or relapse of acute schizophrenia was investigated by Brown and Birley (1968), Birley and Brown (1970). They enquired about events which could be dated to a definite point in time and which usually involved either actual or threatened danger or important fulfilments or disappointments. They distinguished between independent events, which were outside the control of the subject, and possibly independent events, which were not so clearly out of his control but which seemed unlikely to be produced by unusual behaviour of the subject himself. In their main group of patients a significant concentration of independent events (about 60 per cent) was found in the three weeks preceding onset or relapse of schizophrenia. In examining two small sub-groups they found that 4 of 13 patients (31 per cent) who relapsed after reducing or discontinuing phenothiazine therapy had experienced a life event in the three weeks before relapse, compared with 3 of 5 patients (60 per cent) who had been taking phenothiazines regularly at the time of relapse. Although these proportions are very different, the numbers in the groups are too small for the difference to reach significance. Furthermore the groups were not matched in any way, and there may be important differences between patients who discontinue medication themselves and those who carry on taking it regularly.