The effect of physical exercise and vitamin C on iron absorption after oral iron administration was investigated. Eight healthy male subjects without iron deficiency were studied after administration of 100 mg ferric sodium citrate complex, 100 mg ferric sodium citrate complex with 200 mg ascorbic acid, and without iron intake, both under resting conditions and after a 1-h bicycle ergometer test at moderate exercise. Serum concentrations for iron, transferrin, and ferritin were measured before and 30 min, and 1, 2, and 4 h after each administration. Under resting conditions administration of 100 mg ferric sodium citrate led to a significant increase in serum iron concentrations. When ferric sodium citrate was administered with vitamin C, iron values increased significantly further. Ingestion of iron together with physical exercise resulted in a higher serum iron concentration than under resting conditions. The maximum increase, reached after 4 h, was 48.2% with exercise and 8.3% without. In combination with exercise, the addition of 200 mg vitamin C did not further increase serum iron concentration. In conclusion, 1 h of moderate exercise enhanced the rate of iron absorption. Under resting conditions the combination of ferric sodium citrate with vitamin C led to significantly increased postabsorption serum iron concentrations compared with iron administration without vitamin C.