1. Total protein amount and amylase and lysozyme activities were measured in the serum and urine of healthy women and men before and after strenuous exercise.
2. Exercise produced no major difference in the serum activities of amylase and lysozyme.
3. The renal clearance of amylase was unaffected by strenuous exercise, but total protein excretion was markedly increased.
4. Very high values of renal clearance of lysozyme were observed after exercise. This implies that the proximal tubular function of protein reabsorption was specifically affected.