We report two cases of filiform polyposis associated with ulcerative colitis that underwent surgery. Case 1. A 25-year-old man was undergoing treatment for ulcerative colitis for one year. Anemia and malnutrition persisted, and shortness of breath during physical activity was gradually observed. Therefore, he was admitted to our hospital urgently. Colonoscopy revealed extensive inflammatory polyposis from the cecum to the transverse colon and sigmoid colon. Due to impaired passage and no improvement by medical treatment, a total colectomy was performed.Case 2. A 54-year-old woman had repeated relapses and remissions during 13 years of treatment for ulcerative colitis. She was admitted to our hospital with abdominal pain, diarrhea, and bloody stools. Colonoscopy revealed intestinal stenosis due to extensive inflammatory polyposis from the cecum to the transverse colon. Since medical treatment did not result in improvement, and complications of dysplasia and adenocarcinoma could not be ruled out, subtotal colectomy was performed. Pathology revealed fibrovascular cores in both cases, and the diagnosis was filiform polyposis.