Selective drainage method of remnant pancreatic stump (RPS) using latex rubber was devised, and I have obtained a good clinical result for the prevention of postoperative bleeding due to the leakage of pancreatic juice after distal pancreatectomy. In this study, amylase (Am:IU/L) and trypsin (Tr:ng/ml) values in exudate were measured to clarify the actual leakage of pancreatic juice. Thirty-three patients with gastric cancer who underwent total gastrectomy with distal pancreatectomy were chosen for this study; 21 cases of selective drainage (group A) and 12 cases of non-selective drainage (group B). The results are noted below. 1) Both Am and Tr values of group A in the exudate from remnant pancreatic stump were statistically higher than those of group B (p < 0.01). Mean values of group A and group B on the first post-operative day were 25.6 x 10(4) versus 2.6 x 10(4)IU/L (Am value) and 324.4 x 10(4) versus 12.2 x 10(4)ng/ml (Tr value), respectively. 2) The mean values rapidly decreased and bottomed on the sixth postoperative day. 3) Not only total drainage amount of Am (sigma Am: sum of Am value x exudate volume from each drain) but also sigma Tr in group B were markedly less than in group A (p < 0.01). It means that more than 40% of pancreatic juice remained in the abdomen without drainage in group B. In conclusion, effective and active drainage of remnant pancreatic stump for the initial three days at least is important to prevent complications and our selective drainage is one of the excellent methods.