Given the rise in prevalence of autism spectrum disorders (ASD) and the legal requirements for public school districts to implement evidence-based educational interventions, there is an increased need for school districts to train staff to implement these interventions with fidelity. The National Professional Development Committee (2014) and the National Autism Center (2015) have identified multiple evidence-based interventions for children with ASD. Many of these evidence-based practices are based in the principles of applied behavior analysis (ABA). One of these ABA interventions is discrete trial training. The present study assessed the impact of an online professional development program on treatment integrity during discrete trial training. The current study utilized a mixed methods design including both a single subject multiple baseline approach and qualitative analysis of an exit interview. The purpose was to determine if the online training impacted the overall integrity with which discrete trials were being implemented. In addition, the study also sought to understand the participants' perceptions of the training. The results suggest that the training had limited impact on the fidelity of implementation of discrete trial training. However, the participants did report improvements in their ability to implement DTT lesson plans with greater levels of integrity. Suggestions for future research are discussed. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]