In a city where specialist homes for the elderly mentally infirm (EMI) have been extensively developed, a study was carried out to determine if residents in such homes were mentally impaired to a degree intermediate between that of residents in ordinary homes, and those in psychogeriatric beds. The study, using valid measures of cognitive impairment and functional disability, showed that while the proportion of cases of senile dementia was similar in all three settings, the severity of disability was graded in the expected direction. Furthermore, cases of mental illness other than senile dementia were almost exclusively found in the EMI homes and psychogeriatric hospitals. However, one in ten of ordinary home residents suffered from senile dementia of a severity which presented problems to the care attendants and the implication of this finding for the level of provision of psychogeriatric beds is discussed.