Minimally invasive surgery is mandatory for rectal tumors to reduce surgical complications and to improve the quality of life. The conventional transanal procedure is one from of minimally invasive surgery for rectal tumors, but it is still often difficult to reach the middle and upper thirds of the rectum due to anatomical characteristics. Transanal endoscopic microsurgery (TEM) is a technique that allows radical resection of rectal tumors in the distal as well as proximal third of the rectum. Performing radical surgery using this technique requires preoperative estimation of tumor extension both histologically and by X-ray images. It should allow provide safe and radical excision of rectal tumors. In our department, patients with rectal tumors are evaluated for risk factors using barium enema, endoscopic ultrasound, punch biopsy, etc. Fifty patients (rectal cancer, 34: cartinoid, 4: adenoma, 12) have undergone radical TEM. The operation was converted to open surgery in 2 cases because of rectal perforation. Radical open surgery was performed after TEM in 1 patient since cancer invasion was revealed by postoperatively upon histological examination. We conclude that TEM is a useful technique for radical resection of rectal tumors and is associated with a low rate of postoperative complications and a high surgical success rate.