Feelings of unreality occur in many, if not all, cases of depressive psychosis and are so important in the differential diagnosis that the subject merits special consideration. I have observed this symptom in a series of twenty-eight cases and found it to be a distinct feature in the clinical picture. The patients in all but two of my cases were private patients, and opportunity was therefore afforded for careful and continuous observation. The problems in diagnosis centered largely around differentiation between the psychoneuroses and mild mental depressions. Only two patients required hospitalization, and observations were consequently entirely extramural. This factor, in a measure, probably accounts for the prominence of feelings of unreality, since the degree of depression was never sufficiently severe to mask them. Whenever the feeling of unreality was revealed as a symptom it clearly indicated something graver than a psychoneurosis and pointed the way to a more rational