The relation between exercise and absenteeism due to illness and injury was assessed in 21,924 male workers. Exercisers I (engaging in exercise less than once a week), II (once or twice a week), and III (more than three times a week) had a significantly lower incidence of absence than nonexercisers. The proportion of cases of absence in exercisers I, II, and III was 10%, 10%, and 14% lower, respectively, than that of nonexercisers. The number of days absent among exercisers I, II, and III was 48%, 43%, and 26% lower, respectively, than among nonexercisers. Controlling for confounding factors by logistic analysis, significantly reduced relative risk of absence persisted among exercisers I, II, and III versus nonexercisers at 0.88, 0.90, and 0.87, respectively. These findings indicate that worker exercise was associated with absence due to illness and injury.