Summary The chain of events from decreased MAO activity in the peripheral blood of certain schizophrenic patients, particularly paranoid patients, to in creased concentrations of PEA, to increased NE and NE turnover in the brain of schizophrenic patients, may prove not to be as closely linked as the current hypothesis and available data suggest. Nevertheless, the notion that this chain exists is testable and provides an integrated hypothesis of etiology for a subgroup of schizophrenic patients.