SUMMARYA retrospective casenote review was performed on all patients over 65 years of age in one health district who were detained under the Mental Health Act 1983 during the first 6 years of its operation. There were 132 episodes of detention affecting 120 patients. Fifty-three per cent were for organic illness and 47% for functional illness. The organically ill were detained most commonly because the carer was no longer able to cope or, for those living alone, because of self-neglect. The functionally ill were most commonly detained in the interests of their health only. The majority (52/64) of patients with dementia were not discharged to their previous address after being detained, most of these (29/64) being discharged to residential care. Twenty-seven per cent of the whole sample died within a year of being detained, a rate higher than that in the general population. Only nine tribunals were held in the study period.