Preclinical disability in mobility tasks can be recognized by asking people without overt mobility disability whether they have changed the way, either the manner or the frequency, of doing a mobility task because of a health or physical condition. Like other compensatory strategies, preclinical mobility disability has a dual nature as both a risk marker associated with impairment or limitation and a mediating factor affecting the natural history of disability. The method of ascertaining preclinical disability through self-report has been shown to have construct validity, to be reliable, and to identify people at an elevated risk of developing overt mobility disability over 1 to 2 years. Many worthy research questions in this field remain to be addressed, especially regarding qualitative heterogeneity (doing more vs doing less) and interactions among compensatory strategies. Nonetheless, there is sufficient evidence to apply what is known about preclinical disability to screening in clinical settings. This area of research and practice constitutes an opportunity for physical medicine and rehabilitation and geriatric medicine to jointly make a large beneficial impact on population health through strategies to prevent disability because rapidly growing numbers of older adults will experience this early and potentially malleable stage.