In order to examine the descriptive validity of ICD-10 schizophrenia, 1,476 consecutively admitted in-patients were included in the present study. ICD-10 schizophrenia (n = 951) was compared with other non-affective psychotic disorders {[}persistent delusional disorders (n = 51), acute and transient psychotic disorders (n = 116) and schizoaffective disorders (n = 354)] with respect to socio-demographic, symptomatological and other clinical parameters. Analyses revealed that it is possible to distinguish schizophrenia from other non-affective psychotic disorders according to ICD-10 criteria: schizophrenic patients were characterised by more pronounced negative symptoms and a lower global functioning. They were younger than patients with persistent delusional disorders and schizoaffective disorders but older than patients with acute and transient psychotic disorders. The results are in line with a high descriptive validity of ICD-10 schizophrenia and highlight the importance of negative symptoms for this diagnosis. Copyright (C) 2003 S. Karger AG, Basel.