Relative to information on activities of daily living, information regarding the onset of and recovery from mobility difficulty has been limited. Drawing upon data gathered from 6, 376 self-respondents aged 51–61 years at baseline (1992) who were successfully reinterviewed in 1994 as part of the Health and Retirement Survey, the authors were able to build upon and add to knowledge gained from previous studies of the onset of and recovery from mobility difficulty. Hierarchical logistic regression was used to separate the direct and indirect effects of predictors of mobility difficulty onset and recovery at 2-year follow-up. To separate direct and indirect effects, the authors categorized various predictors as being related to sociodemographic factors, economic factors, health behavior, chronic disease, or physical impairment, and the categories were sequentially incorporated into a series of equations. The order in which the predictors were incorporated into the equations followed from a theoretical model of the disability process. In this study of mobility difficulty, the strongest direct predictors of recovery were having little baseline difficulty and the absence of diabetes mellitus, lung disease, and frequent pain. The strongest direct predictors of onset were female sex, less education, low net worth, lack of private health insurance, obesity, and frequent pain. Few indirect predictors for either onset or recovery were identified. Predictors of recovery were few and differed from predictors of onset. Further efforts are needed to identify modifiable predictors among females, persons with few economic resources, and those with frequent pain. Am J Epidemiol 1998; 148: 63–71.