Schizophrenia is associated with impaired cognition, which persists despite current treatments, and is an important determinant of quality of life and overall function. Converging lines of evidence suggest that interleukin-6 (IL-6) is a promising therapeutic target for cognitive impairment in schizophrenia. IL-6 is a cytokine produced by peripheral blood leukocytes, and central nervous system (CNS) microglia and astrocytes. The IL-6 gene is a risk factor for schizophrenia and may impact on serum IL-6 levels. Blood and (cerebrospinal fluid) CSF IL-6 levels are altered in schizophrenia. IL-6 levels are associated with psychopathology3 and cognition in schizophrenia. In populations outside of schizophrenia, higher serum IL-6 levels are associated with poorer cognition. In first-episode and chronic schizophrenia, IL-6 levels are a significant predictor of smaller left hippocampal volume.