The use of antipsychotics, particularly second generation antipsychotics, among children and adolescents has increased markedly during the past 20 years. Existing evidence gaps make this practice controversial and hinder treatment decision-making. This article describes and prioritizes future research needs regarding antipsychotic treatment in youth, focusing on within-class and between-class drug comparisons with regard to key population subgroups, efficacy and effectiveness outcomes, and adverse event outcomes. Using as a foundation a recent systematic review of antipsychotic treatment among youth, which was completed by a different Evidence-based Practice Center, we worked with a diverse group of 12 stakeholders representing researchers, funders, health care providers, patients, and families to identify and prioritize research needs. From an initial list of 16 evidence gaps, we enumerated 6 high-priority research needs: 1) long-term comparative effectiveness across all psychiatric disorders; 2) comparative long-term risks of adverse outcomes; 3) short-term risks of adverse events; 4) differentials of efficacy, effectiveness, and safety for population subgroups; 5) comparative effectiveness among those with attention-deficit/hyperactivity disorder and disruptive behavior disorders and common comorbidities; 6) comparative effectiveness among those with bipolar disorder and common comorbidities. In this article, we describe these future research needs in detail and discuss study designs that could be used to address them.