This pilot study described the effects of a programmed vestibular stimulation on heart rate change in two children with Down's syndrome exhibiting congenital heart defects. The stimulation programme was applied twice weekly for eight weeks. The total amount of controlled rotary vestibular stimulation provided within each trial was approximately 1.5 minutes, and the average intensity of the stimulation was at a frequency of about 0.5 Hz. Heart rate was recorded before and after each programmed stimulation. The two children responded physiologically to stimulation: their heart rate decreased but remained within normal limits. It appeared that autonomic response as indicated by heart rate change and behavioural cues from the two children provided a safety guide for the amount and intensity of the stimulation.