Andreas Rett described a “cerebral atrophic syndrome accompanying hyperammonemia” for the first time in 1966, and by 1983 over 80 such cases had been identified and described not only in Austria but also in other countries. If the information at our disposal is correct, we have reported on what we believe is the first case of a patient with a definite Rett syndrome in the German Democratic Republic. We are, regrettably, still unable to contribute decisively to the clarification of the etiology and pathogenesis of the disease, but will, through further publications and papers at pediatric and child-neuropsychiatric meetings, continue to spread the knowledge of the symptomatology\ It is remarkable that in the present case neither computer tomography nor electroencephalography showed definite abnormalities despite much effort. Definite proof of cerebral atrophy cannot, therefore, yet be furnished. But we still have no doubt that our diagnosis is correct. We intend, within the framework of a joint study being conducted by the University Pediatric Hospital Rostock and the Ludwig Boltzmann Institute, Vienna, as part of the scientific and technical cooperation between the Republic of Austria and the German Democratic Republic, to investigate further the epidemiology and etiology of this disease in cooperation with our Departments of Metabolic Disturbances and Genetics.