 Individuals with schizophrenia often experience disturbing residual symptoms, even with the best available current treatments. Homocysteine, normally found in the body, can interfere with NMDA-glutamate receptor function, and this might be responsible for some of the symptoms of schizophrenia. This double-blind protocol will have study participants who suffer from schizophrenia take either a high-dose combination of folate, B12 and pyridoxine a combination that can lower homocysteine in the body or placebo for three months. Clinical measures e.g., PANSS, CGI will be taken to determine whether those taking the vitamin combination experience clinical benefit. 