The course and prognosis of 20 patients with the syndrome of doubles (syndrome of Capgras, syndrome of Frégoli, syndrome of intermetamorphosis, syndrome of subjective doubles) were studied. The onset of the syndrome occurred either synchronously or at a later stage than the onset of the associated psychosis. The syndrome failed to remit in seven of the 20 cases, and in the others remission occurred either synchronously with or later than the remission of the basic psychosis. In all cases of depression, the syndrome cleared shortly after remission of the depressive illness. It was, however, more persistent than the accompanying psychosis in the schizophrenic patients with the Capgras variety. Relapse of the basic psychotic condition in the setting of which the syndrome had originally developed was invariably accompanied by reappearance of the syndrome.