This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. This project compares, via a multisite randomized controlled trial with double-dummy medication administration, the efficacy, tolerability, and longevity of benefit of two agents, risperidone and valproate, in diminishing aggressive behavior when used adjunctively with stimulant treatment among children who experience demonstrably inadequate response to stimulant monotherapy and behavioral intervention.