<正> The pressure changes produced by firing bullets of 7.62mm and 5.56mmand steel sphere of 1.03g through water and 20% gelatin blocks werestudied.The pressure was measured by a transducer of Model B-J 1000.It was demonstrated that there were three peaks produced when thetwo kinds of bullets were fired through a water tank.The interval betweentwo successive peaks was longer in the waves produced by the 7.62mmbullet than in those produced by the 5.56mm bullet.The peak value ofthe 5.56mm bullet was the largest

that of the 7.62mm bullet the second

and that of 1.03g steel sphere the lowest.The fore-mentioned differences among the pressures produced by differentprojectiles were dependent on their respective ballistic characteristics.Thepressure value detected and the patterns of the pressure changes were closelyrelated to the temporary cavity effect and the characteristics of tissue da-mage.