The compatibility of the classification systems ICD-10 and DSM-III-R w
as investigated in a sample of 100 psychiatric inpatients with severe
affective and psychotic disorders. Four independent raters assessed di
agnoses by means of checklists from psychopathological descriptions of
case records. Congruence between ICD-10 and DSM-III-R was good for de
pressive disorders with agreement rates above 80% and fair for bipolar
disorders with rates above 60%. Less consistent findings were obtaine
d for schizophrenia with rates of 57.5% for ICD-10 diagnoses and 82.6%
for DSM-III-R diagnoses. Agreement for schizoaffective disorder was b
elow 40% and thus insufficient. The results indicate that even small d
ifferences in the definitions of mental disorders may result in consid
erable inconsistencies.