Schizophrenia may result from immune or inflammatory disorders, which are mediated by cytokines. Data in this field are heterogeneous and often contradictory. We investigated circulating levels of IL-6 and TNF-alpha, two distinct proinflammatory cytokines. Using immunoassay, we assessed IL-6 and TNF-alpha in serum from chronic schizophrenic patients (n = 30) and normal controls (n = 15). Circulating levels of IL-6 were higher in patients than in controls; those of TNF-alpha were not significantly higher than in controls. In addition, IL-6 levels were higher in patients with acute exacerbation of schizophrenia than in patients with remissions. Our results suggest that immunologic abnormalities in schizophrenia may be related to a specific inflammatory process mediated by IL-6. An interesting line of research would be the evaluation of IL-6 cerebral production in CSF.