Intussusception in adults is relatively rare. Here we report a 52-year-old man with an extensive colo-colonic intussusception caused by a polypoid mass in the ascending colon. The mass, which was 10 x 8 x 5 cm in size, had been palpated preoperatively and was suspected to be a sigmoid tumor. The patient was treated successfully by reduction of the invagination and subsequent right hemicolectomy.