The clinical findings of seven girls and one woman, 2 to 25 years of age, with Rett syndrome are presented. Previous diagnoses included Prader-Willi syndrome, Angleman syndrome, toxic reaction to pertussis vaccine, CNS dysgenesis, and encephalitis. Rett syndrome has a recognizable neurodevelopmental phenotype without a specific biologic marker, which makes the diagnosis difficult at times. Treatment is largely supportive, and an active parents'' association has been helpful to many families.