Research into factors underlying the dissemination of evidence-based practice is limited within the field of Applied Behaviour Analysis (ABA). This is pertinent, particularly in the UK where national policies and guidelines do not reflect the emerging ABA evidence base, or policies and practices elsewhere. Theories of evidence-based practice in education and policy suggest that decision makers’‘perceptions’ of evidence are significant factors in dissemination. For professionals, scientific evidence is often critical. For others, including parents, experiential and anecdotal evidence can be as important. Within autism education, parents are often, and not necessarily by choice, key decision makers. This study is the first to try to identify and quantify UK parents’ beliefs about ABA in the education and support of children with autism. We developed and tested, using an internet survey method, the Parental Beliefs about ABA and Autism scale (P-BAA). Current and/or past use by parents of any behaviorally based approach including ABA was a significant predictor of P-BAA scores as were parent education, household income and child diagnosis: experience of a behaviorally based approach, higher levels of education and income and children at the more ‘severe’ end of the autism spectrum were associated with more positive beliefs about ABA.