A growing body of research shows that many young children with autism and pervasive developmental disorders can derive significant, lasting, and sometimes dramatic benefits from early intervention based on the principles of Applied Behavior Analysis. This manual, inspired by that research, provides a wealth of practical information for parents, professionals, and others concerned with helping such children. Authors include parents whose children have been the beneficiaries of a science based approach to autism treatment, as well as many noted researchers and experienced clinicians.