Most explanatory models of living arrangements in later life link the decision process surrounding choice of living arrangement to personal resources such as income and health. Applications of these models, however, are based for the most part on crosssectional rather than longitudinal data. In this paper we examine living arrangements in later life among the nonmarried population aged 55 and over, using data from the Survey of Income and Program Participation. We observe individuals as they change living arrangements, die, or become institutionalized. Our results suggest that economic resources dominate the decision-making process in transitions across different household arrangements, whereas health is most important in explaining institutionalization.