While the concept of "challenging behaviour" is socially defined, it often involves persistent behaviour with serious physical and social consequences for the person and others. Challenging behaviour is relatively common amongst people with learning disabilities and often poorly dealt with. Models for understanding such behaviour have developed over time and can now provide a relatively sophisticated account. Such models are of immense use in understanding the behaviour of individuals and have clear implications for the development of individualised interventions. They also have implications for the design and organisation of services which will more competently support people with challenging behaviour and, as far as possible, prevent its emergence in those at risk