The need to understand the role of communication in triggering, maintaining or exacerbating challenging behaviour is crucial when working with a client group with severe learning disabilities. Speech and language therapists are becoming increasingly involved in this process. The Royal College of Speech and Language Therapists (RCSLT 1996), recommend that the most appropriate form of intervention includes: I. facilitating carers in the understanding of the nature and causes of challenging behaviour, particularly in relation to communication 2. facilitating carers in understanding the role of the environment and their own communication in relation to the clients challenging behaviour 3. facilitating carers in developing more appropriate ways of communicating with clients with challenging behaviour 4. Supporting carers in developing appropriate activities for the client (RCSLT I996) This project used the above principles to investigate the effect of speech and language therapy on the communication environment in a home for people with learning disabilities and challenging behaviour. The results show an increase in: the length of interactions initiated by the staff with the service users; the use of non- verbal communication to support interactions and a decrease in the number of attempts the service users needed to make before a staff response was given. The author concludes that speech and language therapy was effective in improving the communication environment. The impact of the improved communication environment on challenging behaviours was not measured.