Two cases with Rett syndrome (RTT) are presented. One of these is a 77-year-old woman. The occurrence of elderly women with diagnosed RTT is sparse; this may be due to the fact that the clinical traits of RTT often are atypical in adult women and the information about early childhood limited. The finding of mutations in the MECP2 gene in many patients with RTT has provided us with a tool for verification of suspected cases. The patient presented here was clinically diagnosed with RTT at the age of 66 years and now the presence of one of the common missense mutations in MECP2 has been demonstrated. Additionally, skewed X-chromosome inactivation was found. It is likely that this woman is the one of the oldest living patients with RTT. The other case is a 30-year-old woman with preserved speech and the MECP2 missense mutation R133C. Possibly this mutation gives rise to a relatively mild phenotype. A survey of the 44 mutations in the Danish patient group is given.