Abstract: Objective To evaluate the relationship between the IL-18 levels and cognitive functionin patients with chronic schizophrenia. Methods We recruited 158 chronic patients and 150 normal control subjectsin our hospital between Jan.2012 and Dec.2014.Repeatable Battery for the Assessment of Neuropsychological Status(RBANS) was used to measure the cognitive level,Enzyme-Linked Immunosorbent Assay(ELISA) was performed to test the peripheral blood IL-18 level,polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was used to detect IL-18 gene-607C/A polymorphism,and Positive and Negative Symptom Scale(PANSS) was used to assess the clinical symptoms of patients. Results IL-18 levels were increased in chronic schizophrenia patients as compared to normal controls (P<0.01).RBANS total score and the subscales of immediate memory and delayed memory were lower in patients than normal controls(all P<0.001).In patients,IL-18 levels were positively associated with RBANS total score and the subscales of immediate memory and delayed memory(all P<0.05).Multiple regression analysis further confirmed that IL-18 was an independent contributor to RBANS total score and the aforementioned two indexes(all P<0.05). Conclusion The immune responses may play an important role in cognitive performance in schizophrenia.Although the underlying mechanisms for the associations of IL-18 with cognitive performance are still unknown,the positive correlations may implicate some potentially neuroprotective effects of IL-18 on cognition in chronic patients.