This pamphlet reviews the historical process involved in initially recognizing Rett Syndrome as a specific disorder in girls. Its etiology is unknown, but studies have considered factors as hyperammonemia, a two-step mutation, a fragile X chromosome, metabolic disorder, environmental causation, dopamine deficiency, and an inactive X chromosome. Characteristics of Rett Syndrome include onset during the second year of life, acquired microcephaly, stereotypical hand movements, ataxia, and a consequent classification as severely or profoundly retarded. Girls with Rett Syndrome have secondary problems such as scoliosis, seizures, respiratory problems, teeth-grinding, communication disorders, and poor motor skills. Some medications have been effective in controlling the seizures, such as "Tegretol,""Depakene,""Dilantin," and "Clonopin-Clonazepam." Special teaching techniques consist of music therapy, swimming therapy, tactile stimulation, horseback riding, etc. Adapted classroom equipment appropriate for use with Rett Syndrome children includes scoliosis jackets, corner chairs and other adapted chairs, bolster rolls, vestibular boards, large balls, and wheelchairs. (JDD)