56 patients with RDC diagnoses of schizophrenia (n = 40) and mania (n = 16) were interviewed with a structured interviewing procedure. The evaluation was performed by 2 raters who were blind for diagnosis. Two instruments were used for evaluation concerning thought and language disorders: the ‘Scale for Assessment of Thought, Language and Communication’ developed by Andreasen and the ‘Endogenomorphic Schizophrenic Axial Syndrome’ by Berner with its emphasis on thought disorders. The interrater reliability for both instruments was found to be good to acceptable for the essential items. A comparison of the frequency of thought disorders according to the two different instruments showed an occurrence of derailment and incoherence of the Andreasen scale in both diagnostic groups, while thought disorders of the schizophrenic axial syndrome were represented only in the group of schizophrenics. This is because in contrast to the Andreasen scale, the presence of pressure of speech is considered as an exclusion criterion for the schizophrenic axial syndrome. Thus, thought disorders according to the schizophrenic axial syndrome are seen to possess diagnostic significance.