Study Locations: The study will be conducted in the Treatment Units for Research on Neurocognition and Schizophrenia (TURNS) study network, which is comprised of seven sites: Columbia University School of Medicine (P.I.: Jeffrey Lieberman, M.D.); Duke University School of Medicine (P.I.: Joseph McEvoy, M.D.); Harvard University School of Medicine (P.I.: Donald Goff, M.D.); Maryland Psychiatric Research Center (MPRC) (P.I.: Robert W. Buchanan, M.D.); Nathan Kline Institute (P.I.: Daniel Javitt, M.D.) University of California Los Angeles School of Medicine (P.I.: Steve Marder, M.D.); and Washington University School of Medicine (P.I.: John Csernansky, M.D.). The TURNS is a NIMH-funded contract for the evaluation of new compounds for the treatment of cognitive impairments in schizophrenia (HHSN 27820044 1003C; P.I.: Steve Marder, M.D.). Data management will be performed by the Clinical Trials Data Management Unit of the Nathan Kline Institute under the direction of Jim Robinson, M.S., and statistical analysis will be performed by Dr. Robert McMahon of the Maryland Psychiatric Research Center. Laboratory assays will be performed by Quest Diagnostics.