The study will consist of two phases: a 4-week continued stability phase (lead-in phase) and a 12-week double-blind treatment phase. In the lead-in phase, subjects receiving antipsychotic medication, who manifest moderate to severe and persistent negative symptoms, will remain on their maintenance regimen for at least four weeks. The treatment phase will be a 12-week, parallel groups, double-blind, placebo-controlled trial of adjunctive rasagiline (1 mg/day), a selective MAO-B oxidase inhibitor.