Relation between leukocyte elastase (LE) activity of peripheral blood and temporal parameters of late cognitive component of event-related potentials (ERP) was studied in 36 patients with different types of schizophrenia and 28 healthy controls. Both P300 latency and amplitude correlated with LE activity in patients, but not in controls. The results suggest a relationship between innate immunity activation and pathophysiologic processes underlying cognitive impairment in schizophrenia. Possible mechanisms of the correlations revealed are analyzed.