['To examine whether the lower risk of institutionalization among older adults living with a spouse as compared with those living alone or with other persons could be explained by socioeconomic factors, housing, and chronic medical conditions.', 'We used population-based follow-up data on Finnish adults aged 65 years and over (N=280,722), covering the period from January 1998 to September 2003, to analyse the risk of entering into long-term institutional care by living arrangements. Kaplan-Meier estimates and Cox regression models were applied.', 'Among men, those living alone had a 70% higher risk and those living with other persons a 56% higher risk of being institutionalized than those living with a spouse, independently of age, region, and urbanicity. The corresponding figures for women were 29% and 21%. Among men, the lower risk of institutionalization among those living with a spouse than among those living alone was partly explained by higher educational level, occupation-based social class, household income, home ownership, house type, better housing conditions, and lower likelihood of having depressive symptoms. Almost the same factors helped to explain the lower risk among women, except that those living with a spouse were not advantaged in terms of education or having fewer chronic diseases.'] Are why older people living with a spouse less likely to be institutionalized : the role of socioeconomic factors and health characteristics?