Serum immunoglobulin levels (IgA, IgG and IgM) were determined by an immunoelectrophoretic method in two separate series of Chinese male schizophrenics and healthy controls. In the first series, 41 healthy male blood donors and 98 schizophrenic patients in different stages of the disease were investigated. In the second series a random sample of 50 acutely ill male schizophrenic patients were investigated along with a second group of healthy male subjects. Serum IgG levels were significantly higher in schizophrenics in both the series (p < 0.001). Serum IgA levels were similar in both the patient and control series. Serum IgM levels were significantly higher in schizophrenic patients having acute or severe illness (p < 0.05 and 0.01, respectively). Serum albumin levels were significantly lower in the patients compared to healthy controls. The above changes in immunoglobulins in schizophrenics were not related to duration or dosage of medication with neuroleptic drugs.