On admission, IgA, IgG and IgM concentrations were determined in 76 schizophrenics, and the correlations of these concentrations to the variables relating to psychopathology, background and prognosis were investigated in the present study, which is a part of a more extensive unpublished study. On the basis of factorization, the highest IgM concentrations were found in withdrawn schizophrenics and the lowest in paranoid schizophrenics. Of the background variables, the patient's present age had a positive correlation and his place of birth (rural-urban) a negative correlation to IgA concentrations, both being at a statistically significant level. IgA and IgM values higher than average at the beginning of treatment predicted a short hospital stay. Earlier, these patients had also needed little hospital care in relation to the duration of the disease. A hypothesis based on the results is presented, according to which a different way of reacting to stress may explain the differences in IgM concentrations in withdrawn and paranoid schizophrenics. The connection between prognosis and immunoglobulins was considered at least partially explainable on the grounds of age at the onset of the disease.