Project Summary/Abstract Although evidence-based treatments (EBTs) have been developed for childhood behavior problems, many families do not have access to these services. Barriers to access include local availability of services, transportation, cost, and perceived stigma. In this project, we aim to test the effectiveness of a mobile health (mHealth) system as a standalone versus coach-assisted intervention with the goal of achieving reach and scalability. The project will consist of an RCT to study the effectiveness of an mHealth system called UseIt! (Utilizing Skills to Enhance the Impact of Treatment) to deliver treatment remotely and promote the use of parent management training (PMT) skills and cognitive-behavioral therapy (CBT) skills. UseIt! is part of the growing field of digital therapeutics, based on the concept that electronic devices can enhance health outcomes and reduce costs. Parents of children (ages 5-8) with disruptive behaviors (N = 324 dyads) will be randomly assigned to Group 1 (standalone app; n = 108), Group 2 (coach-assisted app; n = 108), or Group 3 (control app; n = 108). The outcome assessments (post-treatment and 6-month follow-up) will include measures of target engagement (PMT/CBT skill acquisition and utilization) and symptom reduction. This RCT takes an experimental therapeutics approach and is designed to measure target engagement to determine whether target engagement is associated with symptom reduction. The targets are PMT/CBT skill acquisition and utilization. Skill deficits in these domains are understood as key maintaining factors for serious disruptive behavior problems. Aim 1 is to evaluate the effectiveness of the UseIt! mHealth system as both a standalone and coach-assisted intervention compared to a control app condition. Aim 2 is to assess target (PMT/CBT skill acquisition and utilization) engagement and validation. Aim 3 is to evaluate the effectiveness of the components of the UseIt! mHealth system. The project has the potential to make an impact on both scientific knowledge and clinical practice. In terms of scientific knowledge, the project has the potential to expand our understanding of target mechanisms. By incorporating reliable and valid measures of the treatment targets, the project will be informative regardless of the clinical outcome. In terms of clinical practice, digital therapeutics has the potential to enhance the reach and scalability of skills-based psychosocial interventions. Even small effects can be meaningful on a population level if the intervention can be delivered easily on a large scale at low cost. The project is consistent with NICHD’s mission to ensure “that all children have the chance to achieve their full potential for healthy and productive lives.”