Increased risk of metabolic complications with olanzapine therapy, relative to other antipsychotics, may lead clinicians to avoid its use, despite evidence of greater efficacy. These problems may also pose a therapeutic dilemma for patients who respond well to olanzapine. Metabolic complications negatively impact on morbidity and mortality, impair quality of life and increase illness relapse secondary to medication non-compliance. Thus far, no pharmacologic agent co-administered with olanzapine has proven effective at preventing these untoward effects. The present study proposes to examine the efficacy and safety of metformin to attenuate the metabolic side effects associated with olanzapine.