The ability of glycine to potentiate the NMDA receptor-complex, along with the fact that it is well tolerated in short-and long-term administration, has raised the possibility that it may provide an effective treatment of augmentation for neuroleptic-resistant negative symptoms of schizophrenia. Up to ten children and adolescents, ages 9-18, meeting DSM-IV criteria for schizophrenia, schizoaffective disorder and psychotic disorder not otherwise specified with onset of psychosis by age 12 who have failed at least two prior antipsychotics entering this protocol on their current antipsychotic medication(s) will participate in an open 8-week trial of adjunctive glycine therapy. In addition to the potential benefits, if glycine therapy ameliorates enduring negative symptoms of schizophrenia, we anticipate that recruiting these rare patients will be facilitated by the availability of this new treatment.