This Request for Applications (RFA) solicits applications to study the development or refinement of behavioral, pharmacological or other innovative treatment interventions for individuals with autism or other autism-spectrum disorders. In November 1999, the NIH Autism Coordinating Committee held a workshop to review the state of the field for treatment of autism and to develop recommendations for future National Institutes of Health (NIH) activities and initiatives. A report of this workshop and the resulting recommendations can be viewed at http://www.nimh.nih.gov/research/autismworkshop.cfm. The workshop participants recommended further investigations into areas of basic knowledge that could provide a foundation for treatment development research and called for support of innovative applications linking brain and/or behavioral processes that are at least partially understood with possible interventions. There was also a perceived need for pilot trials for treatments, and treatment efficacy or cost-effectiveness measures in several modalities. These recommendations provided the impetus for this RFA. One intention of the RFA is to encourage the formation of partnerships between investigators familiar with the phenomenology and treatment of autism on the one hand and basic behavioral or neuropharmacology investigators with innovative concepts on the other.