BACKGROUND & AIMS: The relationship between inflammatory bowel disease (IBD) and the incidence and mortality of colorectal adenocarcinoma (CRC) has not been evaluated recently. METHODS: We calculated the incidence and standardized incidence and mortality rate ratios of CRC among adult individuals with intact colons using Kaiser Permanente of Northern California’s database of members with IBD and general membership data for the period of 1998 to June 2010 (data through 2008 were used to calculate mortality). We also evaluated trends in medication use and rates of cancer detection over time. RESULTS: We identified 29 cancers among persons with Crohn’s disease (CD) and 53 among persons with ulcerative colitis (UC). Overall, the incidence rates of cancer among individuals with CD, UC, or in the general membership were 75.0, 76.0, and 47.1, respectively, per 100,000 person-years. In the general population, the incidence of CRC was 21% higher in 2007-2010 than in 1998-2001 (P for trend, <.0001), coincident with the growth of CRC screening programs. The incidence of CRC among individuals with CD or UC was 60% higher than in the general population (95% confidence interval [CI] for CD, 20%-200%; 95% CI for UC, 30%-200%) and was stable over time (P for trend was as follows: CD, .98; UC, .40). During 1998-2008, the standardized mortality ratio for CRC in individuals with CD was 2.3 (95% CI, 1.6-3.0) and 2.0 in those with UC (95% CI, 1.3-2.7). Over the study period, anti-tumor necrosis factor agents replaced other therapies for CD and UC; the rate of colonoscopy increased by 33% among patients with CD and decreased by 9% in those with UC. CONCLUSIONS: From 1998 to 2010, the incidence of CRC in patients with IBD was 60% higher than in the general population and essentially stable over time.