Background: The aim of the present study was to evaluate the effects of the sensory equipment provided in a multi-sensory environment (MSE) and the level of social contact provided on levels of stereotyped behaviours assessed as being maintained by automatic reinforcement. Method: Stereotyped and engaged behaviours of two young people with severe intellectual disabilities were observed while the participants were either in a living room or in a MSE and receiving either high or low levels of interaction from carers. Results: For both participants, levels of stereotyped behaviour were lower in the MSE irrespective of the level of carer attention received, while levels of engagement were higher under conditions of high carer attention in both environments. Conclusions: The results are consistent with the hypothesis that reductions in stereotyped behaviour observed in MSEs are due to the increased levels of specific sensory stimulation provided by such environments. (Contains 1 table and 2 figures.)