In the last 10 years, as part of the push towards greater community provision of services for the psychiatrically disabled in the UK, assessment has assumed a prominent position. A variety of different assessment instruments have been employed, including assessment of patient attitudes and opinions, of the environment, social networks and basic living skills (Carson, 1991; TAPS, 1992). Amongst the differing assessment types, behaviour rating scales have a distinct contribution. They are particularly applicable to group settings such as hostels or hospital wards and have the advantage of being objective, behavioural, able to measure change in functioning over time or due to some intervention; and most importantly, they yield numerical scores which can be assessed against “hard data” in the form of norms or scores from other populations, especially those from other countries.