While behavioural assessment has had wide application in a number of educational and treatment settings, relatively little has been done to develop programmes specifically for use with retardates who have been institutionalized for the treatment of disturbed behaviour. As a result, the development of appropriate procedures for the latter group requires extrapolation from the use of behavioural techniques in other settings. The current literature on behavioural assessment stresses the importance of identifying meaningful response units and their controlling variables, if efficacious treatment programmes are to be mounted. To be maximally useful, assessment must provide a relatively simple description in objective, non-inferential terms of how a patient responds to the demands of daily living. While many reports of treatment programmes focus on the assessment of a single, narrowly defined variable, the occurrence of which can be readily counted, this is not appropriate for the initial assessment procedures of a residential treatment centre. What is required is an omnibus approach which samples the patient's responses to a broad array of environmental situations which are relevant to the centre and its population. A review of available behavioural scales reveals that there are very few reliable omnibus scales available for use with retardates and none which adequately assesses the behavioural concommitants of disturbed retardates. To deal with this group of patients, it is proposed that, initially, two scales be used to sample both normal and maladaptive behaviour. A number of suggestions have been made for implementing behavioural assessment procedures in residential treatment centres, especially for disturbed retardates.