Background & Aims: Predictive and protective factors associated with colorectal cancer in chronic ulcerative colitis are not well described. Surveillance colonoscopy and 5-aminosalicylic acid therapy may mitigate cancer risk, but there is debate because these variables have not been evaluated in the same study. The presence of postinflammatory pseudopolyps and use of other anti-inflammatory medications may be important variables that influence risk, but data are sparse. Methods: Variables associated with colorectal cancer were registered in 188 patients with ulcerative colitis-related cancer and matched controls. Conditional logistic regression, adjusted for age at colitis diagnosis and colitis duration, identified a final set of variables independently associated with colorectal cancer. Results: In the final multiple variable model, the most important factors associated with colorectal cancer were a history of pseudopolyps (OR, 2.5; 95% CI: 1.4-4.6), 1 or 2 surveillance colonoscopies (OR, 0.4; 95% CI: 0.2-0.7), smoking (OR, 0.5; 95% CI: 0.2-0.9) and use of corticosteroids (OR, 0.4; 95% CI: 0.2-0.8), aspirin (OR, 0.3; 95% CI: 0.1-0.8), nonsteroidal anti-inflammatory drugs (OR, 0.1; 95% CI: 0.03-0.5), and 5-aminosalicylic acid agents (OR, 0.4; 95% CI: 0.2-0.9), although the latter was not statistically significant after 5 years. Primary sclerosing cholangitis and immunosuppressive use were not statistically significant. Conclusions: These results suggest that, in a population matched for extent and duration of chronic ulcerative colitis, surveillance colonoscopy and use of anti-inflammatory medications may reduce the risk of colorectal cancer. A history of postinflammatory pseudopolyps appears to be a predictive factor for cancer.