Autistic regression is one of the many mysteries in the developmental course of autism and pervasive developmental disorders not otherwise specified (PDD-NOS). Various definitions of this phenomenon have been used, further clouding the study of the topic. Despite this problem, some efforts at establishing prevalence have been made. The purpose of this review was to cover these topics in the context of topics such as descriptive symptoms, age of onset, effects on physical development and language, and discussions of research specific to etiology and treatment. Current status of the research on the topic and future directions are discussed.