Persons with severe and persistent mental illness (SPMI) commonly experience both Substance Use Disorders (SUDs) and Borderline Personality Disorder (BPD), resulting in serious and complex personal costs and public health problems. Although Assertive Community Treatment (ACT) is efficacious for persons with SPMI, it is less clear the extent to which this approach adequately meets the needs of substance dependent BPD clients. Dialectical Behavior Therapy (DBT) is an efficacious psychosocial treatment for individuals with BPD and co-occurring SUDs. Over the past decade, this combined approach of DBT within ACT has been identified as a promising direction for clinical practice, and more ACT teams are using DBT to work with their most difficult-to-treat clients (including those with BPD and SUDs). Dissemination of evidence-based practices remains a high priority at NIDA. A number of barriers limit accessibility to these effective practices in community-based mental health and substance abuse treatment settings. In line with NIDA's priority to disseminate evidence-based practices, this Phase II grant proposes to substantially expand development of an innovative computer-based training (CBT) program aimed at teaching ACT providers effective DBT strategies to reduce in-session dysfunctional behaviors among their BPD and BPD-SUD clients. Specifically, we propose to expand the content to include more DBT dialectical and stylistic strategies, and will add a variety of case-based scenarios to further facilitate interest and to ensure direct applicability to clinical practice. We will also expand interactive exercises to include extensive performance-based learning opportunities that immerse the learner within the treatment context. We will use an iterative process of development in building all new content, ensuring usability and satisfaction by conducting extensive online reviews and individual interviews with DBT experts, ACT experts, and the target audience (i.e., ACT providers), as well as through """"""""live"""""""" usability tests with ACT providers. We will then move to a test of the program's efficacy and effectiveness using a randomized controlled trial (RCT) comparing the CBT to an enhanced CBT condition that includes expert consultation and an online discussion board. In this RCT, we will evaluate gains in knowledge and recall, as well as self-efficacy among ACT providers in treating their clients with BPD and BPD-SUD. Additionally, we will expand the outcome assessment to include a performance-based role-play between each ACT provider and a mock ACT client. Participants will be assessed pre- and post-training, and at 4- and 12-week post-training follow-up. Assertive Community Treatment (ACT) is an effective service delivery approach for persons with severe and persistent mental illness;however, it is unclear as to whether it is effective for individuals with Borderline Personality Disorder or Substance Use Disorders, a high proportion of who are served by ACT. Dialectical Behavior Therapy (DBT), an effective treatment for individuals with Borderline Personality Disorder and Substance Use Disorders, is often sought after by ACT providers to more effectively respond to the needs of their clients. The intent of this project is to develop and evaluate an innovative computer-based training program that will teach ACT providers various DBT strategies that will ultimately improve clinical outcomes among their clients with these complex needs.