The objective of this study was to determine whether the responses to questions about tiredness in daily activities is an early subjective sign of frailty indicating older community-living adults at increased risk for disability and mortality. Tiredness in daily activities as measured by the Mob-T Scale, maximal power in sustained work, and comorbid diseases were assessed together with sociodemographic variables in a sample of 705 non-disabled, 70-year old men and women surveyed in 1984. Vital status of members was determined prospectively over the next 15 years. Onset of disability was measured at 5-, 10-, and 15-year follow-up. Onset of disability among non-disabled 70-year old men and women was strongly related to tiredness in daily activities at 5- and 10-year follow-up. Scores on the Mob-T Scale were significantly associated with mortality during the aggregate 15-year follow-up period. Multiple stepwise regression analyses not only indicated that tiredness in daily activities is a strong independent predictor of both disability and mortality, but also that tiredness mediates the effects of comorbidity and maximal power in sustained work on disability/mortality. Self-reported tiredness in daily activities is suggested as a basis for identifying vulnerable frail subsets of older adults requiring targeted strategies for prevention.