This briefing paper is intended to provide basic information about the diagnosis, educational programming, and special needs of children and youth with Pervasive Developmental Disorders (PDD), a group of neurological disorders usually evident by age 3 and characterized by impairments in social interaction, imaginative activity, and verbal and nonverbal communication skills, and by a limited number of interests and activities that tend to be repetitive. After an introduction, definitions and diagnostic criteria are provided for PDD and its five component disorders: (1) autistic disorder, (2) Rett's disorder, (3) childhood disintegrative disorder, (4) Asperger's disorder, and (5) pervasive developmental disorder not otherwise specified (PDDNOS). PDDNOS is addressed in some detail, noting the possibility that the disorder is on a continuum with autistic disorder. Symptoms and signs of PDDNOS, such as deficits in social behavior, impairment in nonverbal communication, and unusual behavior patterns, are explained. Problems in the diagnosis of PDDNOS are identified with suggestions. Also addressed are the special educational needs of children with PDDNOS, treatment approaches, and finding a parent support group. (Contains 34 references or additional resources.) (DB)