On the basis of a representative survey carried out in Germany in the Autumn of 1990, hypotheses about the effect of diagnostic labelling on lay beliefs regarding schizophrenic disorders were tested. As expected, labelling the disorder as schizophrenia increased the likelihood that biological factors were considered to be aetiologically relevant, while psychosocial stress, which most often was held responsible without labelling was cited less frequently as a cause. Thus, labelling the disorder as schizophrenia can be assumed to cause lay-aetiological beliefs to more closely approximate theories predominant among psychiatric experts. In addition, both the sufferers themselves as well as their parents were less frequently held responsible for the onset of the disorder. However, with diagnostic labelling the treatment prognosis was assessed less favourably. In sum, our results do not furnish a definite argument either for or against the explicit diagnosing of schizophrenia.