Ulcerative colitis, one of the two main forms of inflammatory bowel disease, is characterized by inflammation of the large bowel with constant involvement of the rectum, and a possible continuous retrograde distribution up to the cecum. Typical macroscopic lesions are mucosal ulcerations, with immune cell infiltration and cryptic abscesses at histology. Ulcerative colitis usually manifests with bloody diarrhea, is associated with a number of extra-intestinal manifestations, and may be acutely complicated by toxic megacolon. Longstanding disease may predispose to the development of colorectal cancer. Therapeutic options include mesalazine, corticosteroids, immunomodulators and biologic agents; however, if these treatments fail, the only available therapeutic choice remaining is the surgical removal of the colon. This review emphasizes novel concepts in the basic aspects of ulcerative colitis, and, in addition to the current clinical and diagnostic knowledge, it also describes new treatment options for this condition.