Low muscle strength is associated with mortality, presumably as a result of low muscle mass (sarcopenia) and physical inactivity. Grip strength was longitudinally collected in 1071 men over a 25-year period. Muscle mass was estimated by using 24-hour creatinine excretion and physical activity values, obtained by questionnaire. Survival analysis examined the impact of grip strength and rate of change in strength on all-cause mortality over 40 years. Lower and declining strength are associated with increased mortality, independent of physical activity and muscle mass. In men <60 years, rate of loss of strength was more important than the actual levels. In men >/=60 years, strength was more protective than the rate of loss, which persisted when muscle mass was considered. Strength and rate of change in strength contribute to the impact of sarcopenia on mortality. Although muscle mass and physical activity are important, they do not completely account for the impact of strength and changes in strength.