Developmental disorders can make significant and lasting progress through early intervention grounded in Applied Behavior Analysis. This manual, written by parents, researchers, and experienced clinicians, offers practical guidance for families and professionals supporting these children. It explains how to evaluate treatment options and distinguish evidence-based methods from unproven approaches, objectively assess a child’s skills and development, and teach a broad range of abilities from basic attentional skills to advanced language and social behavior. It also helps readers understand the qualifications needed for those delivering and overseeing behavioral intervention.