BACKGROUND AND AIMS: A large, national, long-term, longitudinal, multi-purpose study has been launched in Sweden--the Swedish National study on Aging and Care (SNAC). The study involves four research centers collecting data in four different areas of Sweden. METHODS: The study consists of two parts: the population part and the care and services part. In the population part, a large, representative panel of elders in different age cohorts is followed over time to record and describe the aging process from different aspects. In the care and services part, a systematic, longitudinal, individually-based collection of data is performed concerning provision of care and services together with functional ability, specific health care problems, and living conditions of the recipients living in the area. RESULTS: The data collection in the population part of the SNAC is not yet completed. In the present article, some preliminary results are reported from the care and services part. These pertain to comparisons between the participating areas with respect to the prevalence of disability among those receiving care and social services in their ordinary homes and those receiving care in special accommodation. A comparison is also presented with regard to the amount of home help provided to subjects with a given disability. CONCLUSIONS: This project has several advantages. It is expected to generate a rich data base relevant for future research on aging and care and to have a direct impact on the future Swedish system of care and services for the elderly.