Foulds’ model proposing a four-class hierarchical structure of mental illness represents an interesting dimension of psychiatric research and discussion and probably has a significant potential on diagnosis, taxonomy, therapeutics and theory. Psychiatric symptoms were investigated in a group of 244 schizophrenic patients with the purpose of analyzing Foulds and Bedford’s notion that psychiatric symptoms are arranged hierarchically. To achieve this the R (recent) version of the Delusions, Symptoms, States, Inventory (DSSI) was administered in the form of a constructed interview to these patients. The hierarchical arrangement of psychiatric symptoms was verified since a great majority of the cases (80.8%) produced symptom patterns conforming to the hierarchy model. However, patients with duration of illness longer than 10 years reported conforming patterns in a lower percentage (77%), whereas 84.6% of those with a duration of illness less than 2 years reported conforming patterns. The non-conforming patterns were those in which integrated delusions were absent in the presence of delusions of disintegration, neurotic symptoms were absent in the presence of integrated delusions, and dysthymic states were absent in the presence of neurotic symptoms.