Schizophrenia is still all too frequently associated with a chronic relapsing course, poor functional outcome, and decreased life expectancy. The chronicity and refractoriness of this illness is particularly pronounced in early onset schizophrenia (EOS=onset <18 years). Although the limited data suggest that clozapine is the most efficacious option for youth with refractory EOS (Kumra et al. 1996; Shaw et al. 2006; Kumra et al. 2008a,b) it is still underutilized, in part due to a profound negative impact on weight and metabolic parameters. To improve the benefit/risk ratio of clozapine in refractory youth, the development of concurrent interventions to limit cardiometabolic effects and enhance effectiveness is sorely needed. For this reason, other medications, often a second antipsychotic, are commonly combined with clozapine in clinical practice. However, a sound evidence base for this clinical strategy is absent, particularly in youth. To fill this critical gap in knowledge, we propose a 12-week, placebo-controlled trial of clozapine supplementation with aripiprazole in 50 youths (age 10-18 years) with refractory schizophrenia. This study aims to: Specific Primary Aim 1: To test whether the concurrent initiation of clozapine with aripiprazole will result in the reduction of key metabolic adverse events compared to cotreatment with placebo. Primary Hypothesis 1: Compared to placebo, augmentation of clozapine with aripiprazole will lead to significantly less increase in weight and BMI z-score, insulin resistance, and lipid levels. Secondary Hypothesis 1: Compared to placebo, augmentation of clozapine with aripiprazole will lead to significantly less increase in risk markers of coronary heart disease (i.e., C-reactive protein, plasminogen activator inhibitor-1, soluble intercellular adhesion molecule-1, and adiponectin). Specific Secondary Aim 1: To test whether the concurrent initiation of clozapine with aripiprazole will result in greater efficacy compared to cotreatment with placebo. Secondary Hypothesis 1: Compared to placebo, augmentation of clozapine with aripiprazole will lead to significantly greater improvement in BPRS total, positive and negative symptom scores. Secondary Hypothesis 2: Compared to placebo, augmentation of clozapine with aripiprazole will lead to a significantly greater number of patients meeting the criteria for a positive treatment response (i.e., at least a 30% reduction in the BPRS total score AND a score of no more than mildly ill on the CGI). Exploratory Aim 1: To identify mediators and moderators of changes in primary and secondary outcomes, such as patient characteristics, antipsychotic blood levels, and markers of metabolic and cardiovascular health.