In order to quantitate the increase in urinary β(2)-microglobulin after exercise urine samples were taken immediately before and after soccer or judo. The titers of β(2)-microglobulin were measured by radioimmunoassay. The results were: 1. Both the acutual and the corrected β(2)-microglobulin levels increased significantly after exercise soccer, although not before. 2. The total protein tended to be increased after hard exercise soccer. 3. Urinary β(2)-microglobulin levels showed similar tends whether the exercise was soccer or judo.