An increasing number of investigators have been devoting their attention to experimental inquiries into the efficacy of behavior modification with the most severe of the childhood disorders—the childhood psychoses, including early infantile autism. Virtually all of the methods employed in this work to date are direct derivatives of the operant-learning procedures which have been established in the comparative laboratories. The primary behavior disorders of childhood which characterize the subjects of the research discussed in this review have been labeled variously childhood schizophrenia, early infantile autism, and symbiotic autism. The deviant behavior patterns of normal, neurotic, and retarded children have been shown to be readily amenable to the control of various operant-training procedures. The studies are grouped according to the type of basic procedure used—positive reinforcement, active avoidance, or passive avoidance. Lovaas performed a series of well-controlled experiments, the results of which supported many of the implications about children's psychotic behavior derived from the findings of earlier studies.