Challenging behavior (e.g., aggression and self-injurious behavior) is a common concern for individuals with autism and intellectual disabilities. Unfortunately, its occurrence increases the risk of overmedication, restraint and seclusion, and physical abuse and neglect for this population. Although behavior-analytic treatment of challenging behavior can be successful, there has been an increased focus on how behavior analysts can prevent its occurrence through adaptive teaching strategies early in the child’s life. This chapter provides an overview of the literature on challenging-behavior prevention, describes strategies that may be effective at reducing the development of challenging behavior (e.g., teaching functional communication, coping, and tolerance skills at an early age), and concludes with directions for future research.