In this paper the differential diagnostic difficulties in schizophrenia have been considered in the light of the concept of personality- stratification.As a working hypothesis three different strata are distinguished. In addition to the essentially somatic basic stratum, two higher strata are considered, the vital and the psychological strata.It is assumed that the schizophrenic psychosis always reaches beyond the level of the psychological stratum, involving the vital stratum also. Similar appearing symptoms can therefore be discriminated by pointing out their different setting, i. e., the different depth of personality structure in which they occur.A set of criteria are described on the basis of which it is possible to decide whether a given symptom belongs to one or another stratum. By way of illustration, these criteria have been applied to the four most important differential-diagnostic questions, namely differentiation between schizophrenia on the one hand, and psychopathic states, neurosis, manic-depressive psychosis as well as certain exogenous schizophrenia-like pictures on the other.