To solicit pilot effectiveness projects that apply a mechanism-based approach to the development and evaluation of deployment-focused preschool Attention-deficit/hyperactivity disorder (ADHD) interventions. Relevant interventions could consider the unique challenges associated with treating ADHD symptoms and impairments in children under the age of six Interventions may also focus on preventing or forestalling the emergence of co-occurring disorders or additional ADHD symptoms and impairments that predictably emerge later in development.