|Purpose: The aim of this study is to clarify long-term oncological and functional results of ISR for low rectal cancer.Methods: This study included 519 patients with low rectal cancer who received ISR. We evaluated a rate of anus-preservation, profiles of anal function and long-term oncological results.Results: Of all the patients, 379 patients were treated with surgery alone, 54 with preoperative CRT, and 86 with preoperative chemotherapy.We experienced anastomotic leakages with grade I, II and III in 21, 19 and 44 (8%) cases. Of 370 patients with diverting stoma, those who could not receive stoma closure were 15 cases (4%). Mean Wexner incontinence scores after stoma closure were 10.8 points at 1 year, 9.3 points at 3 years and 9.0 points at 5 years and 8% of the patients still remained incontinent in 5 years.Local recurrence rate at 3 years was 5% in p-stage I, 21% in p-stage II and 23% in p-stage III, and as well, 60% in CRM positive, 28% in CRM between 0 and 1 mm, 14% in CRM between 1 and 2mm and 13% in CRM with more than 2mm. CRT had better power for controlling local recurrences than preoperative chemotherapy or surgery alone.Conclusion: Addition of preoperative CRT or securing CRM of 1 mm or more were essential for advanced rectal cancer. A few patients remained severe incontinence after ISR.