This report is based on an investigation into the premorbid characters of 51 patients afflicted with "nuclear schizophrenia" (the nature of course of the disease having been bland in 19, paranoid in another 19, and hebephrenic in 13 cases). The characters in premorbidity may be divided into 3 groups: schizoid (20 cases); reactive-labile (15 cases); and explosive-epileptic (13 cases). The development of all patients afflicted with "nuclear schizophrenia" showed characteropathies conditioned by asynchronism, slowed rate of motor maturation, and affective immaturity. In the bland course of disease a narrowing of interests, one-sidedness, unstability, and quick fatigability are found at an early stage. In the paranoid course of disease a lack of drive was found in development: initiative-less, passive children who subordinated themselves, In the later hebephrenic forms there was found, in development, a weakness in emotional contact with an in the affective response to the environment. The study of characteropathies may contribute to an early prophylaxis.