Standard antipsychotic drug regimens do not fully address the impact of cognitive symptoms associated with schizophrenia. The NMDA receptor has been connected to the pathophysiology of schizophrenia. Memantine is an uncompetitive NMDA receptor antagonist. It is hypothesized that adjunctive therapy with memantine will reduce NMDA receptor hyperactivity, improving signal to noise ratio and thereby improving cognitive symptoms.

Inclusion Criteria:

• DSM-IV diagnosed Schizophrenia or schizoaffective disorder who are on a stable antipsychotic regimen with Brief Psychiatric Rating Scale (BPRS) total score greater than or equal to 26 and greater than or equal to 4 on at least one item

Exclusion Criteria:

• Secondary diagnosis of Bipolar I disorder
• Suicidal history
• Organic brain disease
• Dementia
• History of substance abuse