Background. Chyloperitoneum is the accumulation of lymphatic fluid in the peritoneal cavity. Although uncommon, it has been reported after retroperitoneal lymph node dissection. But the incidence of this complication after radical gastrectomy is unknown. In the present study, we analyzed our patients who underwent D3 dissection for gastric carcinoma and developed chyloperitoneum. Methods. Between June 1999 and June 2002, a total of 134 patients with gastric cancer underwent radical lymph node dissection, performed according to the Japanese Research Society for Gastric Cancer guidelines, as the standard procedure for gastric cancer treatment. Of these patients, 34 underwent D3 lymphadenectomy, and chyloperitoneum was detected in 4 of them. Results. There were three male patients and one female patient. All patients were in stage III according to the International Union Against Cancer (UICC)-TNM classification. In three patient, chyle leakage was noticed during the surgery, and surgical ligation of the duct was performed. Abdominal distension developed in one patient 7 days after the surgery, and chylous ascites was diagnosed. This patient was success-fully treated with fasting and total parenteral nutrition, within 2 weeks. Conclusion. The incidence of chyloperitoneum is not low, and may increase with more aggressive surgery. Surgeons should be aware of this complication after retroperitoneal lymph node dissection, and injured lymphatics must be controlled and ligated intraoperatively. © 2005 by International and Japanese Gastric Cancer Associations.