This guide for parents and service providers contains information on autistic spectrum disorder (ASD) in young children and is the product of a review of research-based programs and models and requirements of the Individuals with Disabilities Education Act. The document begins with discussion of the definition of ASD, possible causes of ASD, and screening for and diagnosis of ASD. The main section explains 10 principles of intervention for young children with ASD. These include: (1) the earliest possible start to intervention is essential; (2) services must be individualized for children and families; (3) children with ASD require intensive engagement; and (4) family involvement and participation is critical. The following section examines approaches to providing services including terminology of behavioral approaches, behavioral approaches, developmental approaches, and approaches used by the Birth to Three System. Next, alternative or complementary treatments are considered with suggested principles for evaluating the treatment of autism and questions to ask regarding specific treatments. Concluding sections note the importance of family support, offer a note for parents by parents, and list questions and answers commonly asked the Birth to Three System by parents of children with ASD. Among 10 appendices are lists of early indicators for screening, checklists, screening and assessment tools, relevant organizations, and resources. (Contains approximately 100 references.) (DB)