OBJECTIVES: To describe the association between frailty and health status, the progression of frailty, and the relationship between frailty and mortality in older men. DESIGN: Cross-sectional and prospective cohort study. SETTING: Six U.S. clinical centers. PARTICIPANTS: Five thousand nine hundred ninety-three community-dwelling men aged 65 and older. MEASUREMENTS: Frailty was defined as three or more of the following: sarcopenia (low appendicular skeletal mass adjusted for height and body fat), weakness (grip strength), self-reported exhaustion, low activity level, and slow walking speed. Prefrail men met one or two criteria; robust men had none. Follow-up averaged 4.7 years. RESULTS: At baseline, 240 subjects (4.0%) were frail, 2,395 (40.0%) were prefrail, and 3,358 were robust (56.0%). Frail men were less healthy in most measures of self-reported health than prefrail or robust men. Frailty was somewhat more common in African Americans (6.6%) and Asians (5.8%) than Caucasians (3.8%). At the second visit, men who were frail at baseline tended to remain frail (24.2%) or die (37.1%) or were unable to complete the follow-up visit (26.2%); robust men tended to remain robust (54.4%). Frail men were approximately twice as likely to die as robust men (multivariate hazard ratio (MHR)=2.05, 95% confidence interval (CI)=1.55-2.72). Mortality risk for frail men was greater in all weight categories than for nonfrail men but was highest for normal-weight frail men (MHR=2.39, 95% CI=1.51-3.79, P for interaction=.01). The relationship between frailty and mortality was somewhat stronger in younger men than older men (P for interaction=.01). CONCLUSION: Frailty in older men is associated with poorer health and a greater risk of mortality.