As the number and proportion of very old people in the population increase, there is a need for improved knowledge about their health and living conditions. The SWEOLD interview surveys are based on random samples of the population aged 77+years. The low non-response rates, the inclusion of institutionalized persons and the use of proxy informants for people unable to be interviewed directly ensure a representative portrayal of this age group in Sweden. SWEOLD began in 1992 and has been repeated in 2002, 2004 and 2011. The survey is based on another national survey, the Swedish Level of Living Survey (LNU), started in 1968 with 10-year follow-up waves. This longitudinal design provides additional data collected when SWEOLD participants were in middle age and early old age. The SWEOLD interviews cover a wide range of areas including health and health behaviour, work history, family, leisure activities and use of health and social care services. Socio-economic factors include education, previous occupation and available cash margin. Health indicators include symptoms, diseases, mobility and activities of daily living (ADL). In addition to self-reported data, the interview includes objective tests of lung function, physical function, grip strength and cognition. The data have been linked to register data, for example for income and mortality follow-ups. Data are available to the scientific community on request. More information about the study, data access rules and how to apply for data are available at the website (www.sweold.se).