Weight gain associated with antipsychotic medication use is a major side effect that limits the tolerability of these drugs. This often significant weight gain adversely affects health, increasing risks for developing cardiovascular disease, diabetes, sleep apnea, cancers of the colon, kidneys, uterus, endometrium and esophagus and osteoarthritis. Beasley and colleagues (1997) reported that 40.5% of olanzapine-treated patients gained more than 7% of baseline weight. Much of the olanzapine induced weight gain occurs early in treatment, and antipsychotic-naïve and young patients (Woods et al., 2002) are particularly vulnerable to this side effect. One of the most promising medications to aid weight loss in patients taking olanzapine is amantadine.