We describe herein our technique of using an ultrasonically activated scalpel (Harmonic Scalpel [HS]) to simplify the procedure of anorectal mucosectomy for ulcerative colitis (UC). This technique was successfully employed to perform restorative proctocolectomy and ileoanal anastomosis (IAA) in ten patients with UC. By using the HS, thermal injury of the internal anal sphincter was avoided during mucosectomy, and we were able to dissect the inflamed mucosa sharply without causing bleeding. HS reduced the operative time and blood loss compared with the traditional forceps-coagulation technique. These results indicate that the introduction of this new scalpel will facilitate an increase in the number of cases of mucosectomy for IAA.