The aims of this article were 1) to describe changes in functional ability from ages 75 to 80 among men and women in three Nordic localities, and 2) to analyze whether these changes are determined by changes in household composition from ages 70 to 75. The present analyses include the persons who participated in the NORA follow-up study of 75-80 year-old men and women in Jyväskylä, Finland (N=243), Göteborg, Sweden (N=226), and Glostrup, Denmark (N=274). Functional ability was measured by tiredness and need for help in Physical and Instrumental Activities of Daily Living (PADL and IADL). Changes in functional ability are described as 1) sustained good, 2) decreased, 3) improved, and 4) sustained poor, and changes in household composition as 1) sustained living alone, 2) from living with others to living alone, and 3) sustained living with others. Number of chronic diseases and home help were included as covariates in the multivariate analyses. A large proportion of men and women had sustained good functional ability from age 75 to 80, but we observed both improvement and deterioration over time. For example, with regard to need for help in PADL: 64/59% of the mer/women had sustained good function, 19/21% deteriorated, 3/6% improved, and 14/14% had sustained poor function. Among the women in need of help at age 75, those who lived alone/became alone had a higher risk of sustained need for help from age 75 to 80 compared to women who lived with others [adjusted OR=4.0 (1.3-12.2/4.4 (0.7-26.9)]. This was not seen among the poor-functioning men. It is concluded that poor-functioning, single-living women are at higher risk of not regaining functional ability compared to cohabiting women.