By measuring urinary trehalase which is localized in renal brush borders, we examined whether tubular dysfunction occurred or not during and after normal pregnancy. Urinary trehalase activity in 1st trimester, 2nd trimester, and 3rd trimester was increased significantly as compared with the controls (=non-pregnant women) (p less than 0.01). After delivery, urinary trehalase activity in puerperal 5th day was decreased to the level of the 1st trimester, and the activity of puerperal on the 30th day was in the range of the control value. Urinary beta 2-microglobulin (beta 2-MG) in the 1st trimester and 2nd trimester was not increased significantly as compared with the controls. Urinary beta 2-MG in the 3rd trimester, however, was significantly higher than that in the controls. After delivery, the value for beta 2-MG in puerperal on the 5th day was not decreased significantly as compared with the 3rd trimester, and in puerperal on the 30th day, urinary beta 2-MG was decreased to the control value. Urinary N-acetyl-beta-D-glucosaminidase (NAG) in the 3rd trimester was significantly higher than that in the controls (p less than 0.01) and in the 1st trimester (p less than 0.02). After delivery, a significant decrease was observed in urinary NAG between 5th puerperal day and the 3rd trimester. Moreover, urinary NAG on the 30th puerperal day was the level of the controls. On the basis of these results, it is inferred that tubular dysfunction is observed during normal pregnancy.