Providing intensive early intervention is critical to maximizing outcomes for children with autism spectrum disorder (ASD), and evidence suggests that the earlier intervention can begin, the better the outcome. The first purpose of this article is to review the earliest indicators of ASD in very young children-social and communication impairments-which have important implications for early identification. The second purpose is to review evidence-based intervention practices for children with ASD and to develop a set of guiding principles for providing intervention for infants and toddlers who are at risk for ASD. Issues that are delineated include providing intervention in natural environments, supporting families in early intervention, and embedding intervention in daily routines.