This is a clinical trial of a novel intervention, Behavioral Therapy for Irritability and Aggression (BTIA), for adolescents on the autism spectrum. The main goals of BTIA are to help adolescents develop emotion regulation skills to handle frustration and to strengthen skills for navigating the challenging and diverse experiences associated with the transition to adulthood. The study will test whether BTIA can be helpful to adolescents on the autism spectrum and to their families.