Abstract: Objective: To investigate the clinical characteristics and prognosis of patients with synchronous gastric and colorectal cancer. Methods: Clinical and pathological data of 3416 cases with gastric cancer and 3109 with colorectal cancer, from March 1985 to May 2005, were analyzed retrospectively. Results: Thirteen cases were confirmed as synchronous gastric and colorectal cancer and the incidence of the disease was 0.38% in gastric cancer cases and 0.42% in colorectal cancer. Of patients suffering from synchronous gastric and colorectal cancer, 15.4% were diagnosed before the first operation and 33.3% were not diagnosed with the second cancer until it was radically dissected. The 3-year survival rate of the patients was 30.8% but no patients survived beyond 5 years. Conclusion: The preoperative diagnosis rate of the synchronous gastric and colorectal cancer, the radical dissection rate of the second cancer and the 3-year survival rate after surgical removal of the second cancer were rather low. The key for enhancing the radical dissection rate of the second cancer and the survival rate after surgery for the second cancer lies in the diagnosis rate before the first operation.