Autism is currently one of the most prominent and widely discussed human conditions. Its increased prevalence has intensified the demand for effective educational and therapeutic services, and intervention science is providing mounting evidence about practices that positively impact outcomes. The purpose of this report is to describe a set of practices that have clear evidence of positive effects with autistic children and youth. The report is the third iteration of a systematic review that has examined the intervention literature (Odom, Collet-Klingenberg, et al., 2010 (see EJ903737); Wong et al., 2014; 2015 (see EJ1065197)), extending the coverage to articles published between 1990 and 2017. Chapter 1 discusses the current conceptualization of autism, explains the differences between focused intervention practices and comprehensive treatment models, provides a rationale for narrowing this review to the former, describes other reports that have identified evidenced-based practices, briefly describes the previous reviews, and lastly provides the rationale for conducting an updated systematic review. Chapter 2 describes in detail the methodology followed in searching the literature, evaluating research studies, and identifying practices. Chapter 3 reports the results of the systematic review. It describes the practices along with the type of outcomes they generate and the age of children and youth for whom the outcomes were found. For the first time, race and ethnicity data of study participants are highlighted, and features of the intervention setting and group size, along with the intervention implementer are described. Finally, Chapter 4 summarizes the findings, discusses their relationship to other reviews, compares the current review process to the previous process, identifies limitations of this review, and proposes implications of study results for practice and future research. In the Appendix, each practice is described and specific studies that provide empirical support for the practice are listed. [This report was prepared by the National Clearinghouse on Autism Evidence and Practice Review Team within the Frank Porter Graham Child Development Institute. Additional funding for this work was provided by the Ireland Foundation.]