Rett syndrome is a neuro-developmental disorder that almost exclusively affects females. In addition to neuro-developmental regression and loss of hand skills, apraxia, deceleration of head growth, and increasing spasticity and scoliosis, a number of behavioural features are also seen, including stereotypic hand movements, hyperventilation and breath holding. The aim of the study was to investigate the extent to which analogue environmental conditions affected the frequency of repetitive hand behaviour in eight girls and young women with Rett syndrome. -The frequency of repetitive hand movements was observed every 10 s for four 4-min sessions under the following conditions: Continuous Adult Attention, Adult Demands, Stimulation and No Stimulation. -The frequency of repetitive hand movements was high they occurred in above 60% of all intervals in all conditions for all participants and at nearly 100% for some participants in some conditions. For one participant the frequency of repetitive hand movements was somewhat reduced in the Stimulation condition; for another it was relatively increased in the No Stimulation condition. Overall, environmental manipulations had relatively limited effects on repetitive hand behaviours. Repetitive hand behaviour in Rett syndrome may be maintained by automatic reinforcement or neurochemical processes and may not be primarily influenced by contingent reinforcement.