Systematic data from a multidisciplinary clinical assessment of a large series of females with Rett syndrome (RS; n=87) is presented. Participants’ ages ranged from 2 years 1 month to 44 years 10 months. Areas assessed included oromotor skills, feeding problems, growth, breathing abnormalities, mobility, postural abnormalities and joint deformities, epilepsy, hand use and stereotypies, self-care, and cognitive and communication skills. Many previously reported trends in the presentation of RS over time were confirmed, notably the increasingly poor growth and near pervasiveness of fixed joint deformities and scoliosis in adulthood. In contrast, there was a slight trend towards improved autonomic function in adulthood, whereas feeding difficulties increased into middle childhood and then reached a plateau. Improvements in mobility into adolescence were followed by a decline in those skills in adulthood. Levels of dependency were high, confirming findings from previous studies. Despite the presence of repetitive hand movements, a range of hand-use skills was seen in individuals of all ages. Cognitive and communication skills were limited, but there was little evidence of deterioration of these abilities with age. These findings confirm that RS is not a degenerative condition and indicate that intervention and support to maintain and increase motor skills, daily living skills, and cognitive and communicative functioning are appropriate targets for individuals with RS.