Young children with ASD often present with a range of behavior problems, including aggression, tantrums and difficulty transitioning between activities. Interventions based on the principles of applied behavior analysis (ABA) have been shown to offer an effective means of addressing many of these concerns. Parent-Child Interaction Therapy (PCIT) is a research-supported parent coaching intervention that has been found to be highly effective among typically developing preschoolers presenting with a range of mental health concerns. It also holds considerable promise as a potentially effective treatment for children with ASD. The focus of PCIT is to both improve parent-child interactions and to reduce child behavior problems. PCIT involves the coaching of parents in real-time using a one-way mirror and a “bug-in-the ear device” that allows the therapist to provide feedback and directions to the parent while interacting with his/her child. The first goal of this project is to determine if the PCIT treatment manual can be successfully utilized for preschoolers with ASD and their parents and to evaluate the manual’s ability to decrease problem behavior. It is expected that the current manual will require few modifications for use among preschoolers with ASD. The second aim of this project is to demonstrate that parents and children who undergo PCIT training will see greater improvement on measures of behavior and parenting stress than a group of parents and children who are placed on a treatment waiting list (i.e., do not receive immediate treatment). The investigators plan to recruit a total of 20 families of children with ASD (ages 2.6-6 years) who will be randomized (like flipping a coin) to either PCIT training or a wait-list control group. Treatment will involve 20 weekly, one-hour parent-child coaching sessions. In the future, the investigators are interested in extending research on PCIT to include school-age children with ASD and intellectual disability and to also assess the individual and combined efficacy of PCIT and psychopharmacological treatment in this population.