Colitis-associated colorectal carcinoma (CRC) accounts for about 5% of all CRC and the risk for CRC in inflammatory bowel disease (IBD) patients - according to older meta-analyses - is slightly increased when compared to normal population. Effective anti-inflammatory therapy seems to decrease this risk. Main risk factors for colitis-associated CRC are pancolitis, duration of colitis and presence of primary sclerosing cholangitis. In contrast to sporadic CRC, a characteristic adenoma-carcinoma sequence in the pathogenesis of colitis-associated CRC cannot be found. Nevertheless, numerous cell and gene defects occur. Reactive oxygen species also seem to play a pivotal role in the pathogenesis of colitis-associated CRC. Particularly patients with chronically active pancolitis should undergo regular surveillance colonoscopy, since prognosis of colitis-associated CRC is poor.