In recent years increasing interest has centered on the elderly psychogeriatric patient living in the community and the part played by relatives in supporting these patients. There is a need, however, for ways of assessing the behavioural disturbance shown by such patients at home and the effect this behaviour has on relatives. Ratings by relatives of the behaviour at home of elderly dementing patients attending a geriatric psychiatry day hospital, together with the relatives' own ratings of the degree of stress and upset being experienced were obtained. Using the technique of factor analysis was shown that the patient's behaviour and the relative's reaction could be analysed into a number of separate categories and that these were differentially related to each other. Thus, for example, personal distress in the relative was related mainly to the amount of apathetic and withdrawn behaviour shown by the patient, whereas negative feelings held by the relative towards the patient were related only to the degree of disturbance of the patient's mood. The construction of scales measuring these different aspects of patient's behaviour and relative's reaction is described.