Public health aspects of Alzheimer's disease and related disorders (ADRD) are reviewed and their implications for clinical memory testing discussed. We draw attention to its high and increasing prevalence; the substantial extent to which it accounts for morbidity and mortality rates among the elderly; the high costs of caring for victims with respect to both public and private expenditures, i n terms not only of material but also of human resources. The public health aspects of ADRD have specific relevance to the field of clinical testing of memory. Particular issues discussed include the need for more precise epidemiological and other research data, for descriptors of the disease and its consequences that adequately reflect its attendant disability and service needs, for avoiding costly and distressing misdiagnosis or unnecessary admission to institutions, and for systematic assessment that will enable the service system to work in a more coordinated and efficient manner.