The major objective of this research is the attempt to elucidate behavioral mechanisms of antipsychotic drug action in chronic schizophrenics. To this end a strategy of examining in parallel the time course of antipsychotic drug effects upon the symptomatic expression of schizophrenic psychopathology and upon such psychological processes (attention, information processing, somatic arousal), in which deficit or deviant functioning in chronic schizophrenics has been established is being pursued. It is thought that from the temporal order of drug effects upon symptoms and deficit functioning and their interrelationship drug mechanisms of action may be deduced. Moreover, insofar as the relationship between clinical symptomatic course and psychological deficit (and deviance) is under examination, the research has the potentiality of shedding some light on the mediating mechanisms of psychopathology in schizophrenia. A subsidiary objective is the prediction of relapse probability upon drug-discontinuation from drug effects on deficit dimensions reflected in performance measures. A first investigation designed to achieve the above stated aims has been completed and the results partially analyzed. A second investigation, which among other aims, is to serve as a replication of the first in an independent sample of chronic schizophrenic patients is underway. Extended support for an additional year, to permit completion of the second investigation, is sought in this application.