Studies of disability in old age have focused on gross measures of physical functioning. More useful results for prevention might be gleaned from examining risk factors associated with frailty, a concept implying a broader range of more subtle problems in multiple domains. This study conceptualized frailty as involving problems or difficulties in two or more functional domains (physical, nutritive, cognitive, and sensory) and analyzed prospective predictors. Subjects were 574 Alameda County Study respondents age 65-102. One-fourth scored as frail; there was no gender difference. Frail persons reported reduced activities, poorer mental health, and lower life satisfaction. Cumulative predictors over the previous three decades included heavy drinking, cigarette smoking, physical inactivity, depression, social isolation, fair or poor perceived health, prevalence of chronic symptoms, and prevalence of chronic conditions. By modifying these risk factors, it may be possible to postpone the onset of frailty or ameliorate its further development.