Managing challenging behavior in autism spectrum disorders (ASD) can profoundly improve quality of life for children and families. However, many families lack access to research-based treatment, such as applied behavior analysis (ABA). This study is a randomized trial comparing outcomes of treatment for ASD using either a standard Functional Analysis Plus Functional Communication Training (FA+FCT) package or a pragmatic version that offers a briefer, less time-intensive model of FA+FCT. Both types of FA+FCT are provided via telehealth in family homes to maximize generalizability to real-life settings. Providing ABA through telehealth makes an effective treatment accessible across geographic barriers so that no child is excluded based on where they live. The study also examines key family factors that influence successful outcomes. Objectives: The main objective of this study is to determine the most efficient way for families to reduce problem behavior in their children with autism. The study has 3 primary aims: (1) To assess outcomes for ABA telehealth by assigning children to either a Pragmatic FA+FCT group or to a group receiving Standard FA+FCT. Outcomes will be compared based on the percent reduction in problem behavior, communication increases, time to achieve outcomes, treatment fidelity, family acceptance of treatment, and generalization and maintenance of treatment gains. (2) The study will assess the relation of family factors to treatment efficacy and acceptability by assessing parent stress, mood, and social support in relation to outcomes. (3) Cost effectiveness will be assessed in relation to the treatment methods used and the efficiency of ABA telehealth. Methods: The study will include 102 children who are 18-83 months of age, have a confirmed ASD diagnosis, and have serious behavior problems requiring treatment. Thirty-six children will receive intervention in each of three states: Iowa, Georgia, and Texas. Study design is a randomized trial using an intent-to-treat analysis. Half of the sample will be randomized to Pragmatic FA+FCT and half to Standard FA+FCT. Treatment will be provided via telehealth using FCT, which is a function-based ABA technique in which parents are trained to be therapists under the direction of behavior consultants. Study procedures typically are completed within 6 months, and follow-up assessments occur 6 months after treatment completion. Data analyses include comparisons between assessment groups, single-case designs examining responses in individual children, cost analyses, and regression analyses of the effects of family factors on outcomes. Impact: Our prior research shows that problem behavior can be reduced by over 90% in most children with ASD after 4-6 months of telehealth treatment. If Pragmatic FA+FCT can reduce problem behavior at rates comparable to Standard FA+FCT, then treatment can be started sooner and families can achieve successful outcomes at lower cost. Although pragmatic FA+FCT provides less behavioral information, it may be more resistant to treatment relapse because it does not involve reinforcing high rates of problem behavior.