A recent Google Scholar search of “Evidence-based Practice and Autism” yielded 127,000 articles, PsychInfo identified a more modest 1145, PubMed listed 634, and ERIC, the most conservative of the lot, cited 534. Clearly there is much interest and scholarly activity dedicated to the identification of scientific evidence that would inform practices for children, youth, and adults with autism. Emerging from the dark days of the field when mothers were the blame for autism and “parentectomies” were thought by some to be a scientific treatment of choice, the field now looks to rigorous applied science to guide the actions of practitioners. Scholars now employ standard procedures for conducting systematic reviews that provide syntheses of the literature. The purpose of this chapter is to examine this knowledge-generation process and its relevance for the services that impact the lives of autistic individuals. We begin by defining what we mean by “practice” and “practices” and discuss the evolution of systematic reviews over the years. Next, we describe briefly our own systematic review, the increasing complexity of practices, the emphasis on participant characteristics and features of implementation, and the future role of systematic reviews in evidence-based practices for children, youth, and adults with autism and their families.