There is no evidence that using more than one antipsychotic drug enhances clinical efficacy. Nonetheless, this practice is highly prevalent (up to 1/3 of our patient population), and physicians are reluctant to reduce patients' treatment to a single antipsychotic drug for fear of precipitating relapse. This study therefore seeks to evaluate the effectiveness of continued treatment with more than one antipsychotic drug using a rigorous placebo-controlled design. The results of this study will subsequently serve to guide physicians in making appropriately informed decisions regarding the continuation of multiple antipsychotic drugs.