The purpose of this paper is to discuss possibilities for developing operational criteria in psychopathological states and to identify the parameters that differentiate psychotic patients. Statistical analysis was performed in the first step with the aid of factor analysis with extraction of syndromatic characteristics of so-called psychopathological basis syndromes. By cluster analysis in the second step we found out more approaches to a differentiated definition of psychotic states. The classification of individuals into 'natural' and not preestablished groups enabled the construction of descriptive psychopathological algorithms to determine ICD-9 diagnosis within the limitations of descriptive psychiatry.