Background/Purpose: The incidence and natural history of postoperative chylous ascites are not well understood. This complication causes malnutrition and prolonged hospital stay. We investigated our institution’s experience involving chylous ascites, especially following pancreatectomy. Additionally, we designed a new intraoperative method dubbed the ‘milk test’ for preventing chylous ascites. Methods: Five cases of chylous ascites following pancreatectomy from April 2001 through March 2004 were studied retrospectively. The milk test was carried out prospectively. Such rates as positivity and incidence of ascites were examined. Results: Of 65 cases (40 pancreatoduodenectomy; 25 distal pancreatectomy), 5 (7.7%) developed chylous ascites following pancreatic resection. All cases underwent octreotide and total parenteral nutrition treatment. From April 2004 through March 2009, the milk test was used in 104 cases. Surgical procedures comprised pancreatoduodenectomy (n = 78) and distal pancreatectomy (n = 23). Of these cases, 23 (22.1%) tested positive. No significant difference in positive rates was observed between the procedures and diseases. After initiation of the milk test, chylous ascites incidence decreased from 7.7 to 2.9%. Conclusions: For chylous ascites, octreotide and total parenteral nutrition treatments are useful. However, the milk test was found to be a safe and effective method for prevention of chylous ascites following pancreatectomy.