Abstract: Serum pancreatic polypeptide （PP） both at fasting state and after giving compound datura stramonium suppository were measured by RIA in 21 cases of bronchial asthma and 16 cases of chronic bronchitis during attack. In comparison with age-matched control groups the mean basal levels of PP in asthma and chronic bronchitis were significantly higher, which were normalized or nearly normalized after auppression by using compound datura stramonium. The results show that vagal hyperfunction exists in these two diseases during attack and serum PP is a usful biochemical index in monitoring them.