After more than 90 years of research in which the presence or absence of a diagnosis of schizophrenia has been used as an independent variable, little of certainty has been found out about the aetiology of the hypothesized schizophrenia disease process. One possible reason for this lack of progress is that schizophrenia is not a valid object of scientific inquiry. Data from published research (mainly carried out by distinguished psychiatrists) are reviewed casting doubt on: (i) the reliability, (ii) the construct validity, (iii) the predictive validity, and (iv) the aetiological specificity of the schizophrenia diagnosis. It is argued that continued research into the aetiology of schizophrenia is likely to prove fruitless and that psychologists should adopt alternative methods of studying psychosis. Two alternative strategies--the development of empirical methods of psychiatric classification and the study of individual symptoms--are discussed.