Schizophrenia is a chronic disease which begins during early adulthood and persists throughout life. It may appear in two main clinical patterns: chronic progressive and relapsing-remitting. The diagnosis is based entirely on clinical data, as no auxiliary laboratory tests are available. Schizophrenia has a heterogeneous clinical expression which may reflect different etiological factors, such as genetic susceptibility, dysfunction of different neurotransmitter systems or environmental, stressogenic and interfamilial influences. Recently, an autoimmune hypothesis has gained acceptance, which proposes that schizophrenia is one of a spectrum of neuropsychiatric diseases in which an autoimmune attack on the brain occurs. It is also possible, however, that the immunological changes seen in schizophrenic patients are secondary to the disease itself. The main evidence supporting an autoimmune hypothesis is the presence of immunological alterations in schizophrenia that also occur in other autoimmune diseases, e.g. an elevation in serum immunoglobulin levels, a decrease in mitogen responses, morphologically abnormal lymphocytes, an increase in antibrain antibodies, an increase in antibodies to nuclear factor, and a decrease in CD4+ T cells. An autoimmune etiology, if proven correct in the pathogenesis of schizophrenia, would have potential implications for the direction of future psychopharmacological therapies.