Malignant cologastric fistulas are relatively rare. The fistulas probably result from the contiguous growth of a tumor or tumors as they permeate and penetrate all layers of the adjacent viscus and because of the behavior characteristics of mucinoid tumor types under going avascular necrosis aided by digestion of gastric juices. An almost constant finding in cases of cologastric fistulas originating from the colon cancer is that the tumors are bulky, infiltrating, and associated with a marked inflammatory reaction. Formation of the fistulous communications depend on the anatomic locations of the primary tumor. We experienced three cases of malignant cologastric fistulas recently, and we report these three cases.