Empirical findings are reported concerning the relationship between psychoorganic deterioration in old age and the course and clinical symptoms (delusions, presenting symptoms) of the so-called late schizophrenias. The probands were reexamined in their senium decades after the onset of the illness. A significant relationship was found between severe psychoorganic deterioration occurring in old age and a chronic course of the psychoses, generally and particularly in the senium, and between severe psychoorganic deterioration and the occurrence of schizophrenic thought-disorder as the main symptom. Absent or slight psychoorganic deterioration in old age was found significantly co-related to manic-depressive dysthymia as the main symptom. Further development of delusions appears to be independent of the degree of psychoorganic deterioration in old age.