The study evaluated the usefulness of 48 hours of Restricted Environmental Stimulation Therapy (REST) as a treatment for eight autistic children (between 5 and 11 years old). Ss were placed in a dimly lit room which contained only a mattress, told to ask for toilet facilities when needed, and then left alone except for when meals were brought in. A battery of psychological tests was used to assess treatment effects and included Goodenough-Harris Drawing Test; Boehm and Slater Cognitive Skills Assessment Battery; Peabody Picture Vocabulary Test; Krug, Aric, and Almond Autism Screening Instrument for Educational Planning; Educational Subtest; Modified Autism Behavior Checklist; and Leiter International Performance Scale. Three control Ss spent the 48 hours in the hospital ward setting being cared for by parents. REST Ss improved on self initiated communicative speech for the 2 weeks following treatment and improved performance on discrimination learning tasks for 2 weeks. Analysis of behavioral records kept by Ss during the REST session allowed for the identification of the child's most prominent behaviors without interference from distractors or social interaction. It was concluded that REST was nonaversive to autistic patients and appeared to have at least short range beneficial effects. (DB)