Effects of cycle ergometer exercise (approximately 75% maximum ventilatory O2 consumption for 30 min) on the concentrations of zinc and related proteins in erythrocytes and/or plasma were studied on 11 sedentary male students. Lower concentrations of total zinc and of zinc derived from carbonic anhydrase I type (CA-I) in erythrocytes were observed immediately after exercise, but they disappeared after 30 min of rest. The change in total zinc concentration in erythrocytes correlated well with that in CA-I concentration immediately after exercise, as well as after rest. The concentration of carbonic anhydrase II type (CA-II)-derived zinc did not vary substantially at any time. On the other hand, there were significant increases in the plasma concentrations of total zinc and of alpha 2-macroglobulin (alpha 2-MG)-bound zinc immediately after exercise, whereas no such effect was noted in albumin-bound zinc. A positive correlation was found between total zinc and alpha 2-MG concentrations in plasma immediately after exercise. In addition, the change in the activity of alkaline phosphatase, a zinc metalloenzyme, correlated well with that in the total zinc concentration in plasma. These results suggest that a brief physical exercise induces the movement of zinc into plasma.