Ulcerative colitis can be cured by surgery, and the question of how long conservative therapy should be maintained can be easily answered. It should last as long as there is no indication for surgery. In cases of a colitis-associated cancer, the indication is already the presence of low-grade dysplasia. Rectal cancer can be resected and reconstructed with an ileoanal pouch in UICC I and II down to 3 cm from the dentate line. In cecal tumors lymphadenectomy should be performed under preservation of the ileocolic artery. As for refractory colitis an active course of more than 2-4 episodes per year should not be tolerated and permanently active colitis for no more than 6 months. Surgery is also indicated in emergencies with intractable bleeding after a transfusion of more than 4 units of blood and in toxic courses after therapy-resistance for more than 48 h.