By many estimates the majority of adults over age 65 have two or more chronic medical conditions (multimorbidity) and are consequently at increased risk of adverse functional outcomes. Nonetheless, many older adults with multimorbidity are able to maintain high levels of function and retain good quality of life. Research presented here is designed to understand the influences that help ensure better functional outcomes in these older adults. This chapter presents findings that draw on data from the Midlife in the United States study. The independent and interactive contributions of diverse factors to multimorbidity and changes in multimorbidity over time are reviewed. The degree that multimorbidity increases risk of cognitive impairment and disability is examined. The role of inflammation as a mediator is considered. Multimorbidity is increasingly the norm for older adults, so better understanding of factors contributing to variability in multimorbidity-related outcomes can lead to improved quality of life.