The most important factors that determine treatment strategy in ulcerative colitis (UC) are disease extent and severity. Orally-topically administered 5-aminosalicylates (5-ASA) remain the treatment of choice in mild-to-moderate UC. In contrast, the treatment of refractory (to steroids, azathioprine or 5-ASA) and fulminant cases is still demanding. New evidence supports a role for infliximab induction and/or maintenance therapy in these subgroup of patients leading to increased remission and decreased colectomy rates. The aim of this paper is to review the rationale for the use of TNF-alpha inhibitors in the treatment of UC.