Childhood-onset schizophrenia (COS), particularly when diagnosed prior to the age of 13, is considered to be especially rare and severe. This article provides an in-depth look into its symptomatology, general course, long-term functioning, diagnostic criteria, and methods of assessing the disorder. It also includes discussions of the various treatments used with patients having COS, including psychopharmalogical treatments, cognitive therapy, family interventions, educational interventions, and environmental manipulations. Particular attention is paid to the educational implications of the disorder and the role of school psychologists in working with this population. © 2004 Wiley Periodicals, Inc. Psychol Schs 41: 803–811, 2004.