In order to evaluate iron balance in the human body, we studied the effects of exercise on iron excretion in urine, sweat and feces. The subjects were five healthy male, college athletes. The daily intake of nutrients by the subjects was regulated by a prescribed diet (Calorie Mate, Ohtsuka), and the control measurements and the exercise measurements were performed within seven days. Excretion of iron in the urine during the exercise period was significantly higher than in the control period. The excretion of iron in the sweat was 1.076±0.118 mg, i. e, , about 70% of total iron physiologically excreted from the human body. The excretion of iron in the feces during the exercise period was significantly lower than during control period. Feces volume was positively correlated with energy expenditure and negatively correlated with the excretion of iron in the feces. Iron absorption during the exercise period was significantly higher than during the control period. These findings suggest that exercise stimulates not only iron excretion via urine and sweat, but iron absorption, and that iron balance remains positive in healthy male subjects who have normal iron status.