AIM Surgery aims to prevent cancer-related morbidity for patients with ulcerative colitis (UC) associated dysplasia. The literature varies widely regarding the likelihood of dysplastic progression to higher grades of dysplasia or cancer. The aim of this study was to characterize the likelihood of the development of colorectal cancer (CRC) of patients with UC-associated dysplasia who chose to defer surgery. METHOD A retrospective review was carried out of patients undergoing surgery for UC at the Mayo Clinic, who were diagnosed to have dysplasia between August 1993 and July 2012. The relationships between grade of dysplasia, time to surgery and the detection of unsuspected carcinoma were investigated. RESULTS In all, 175 patients underwent surgery at a median of 4.9 (interquartile range 2.5-8.9) months after a diagnosis of dysplasia. Their median age was 52 (interquartile range 43-59) years. An initial diagnosis of indeterminate dysplasia was not associated with CRC [0/23; 17.7 (8.1-29.6) months]. Thirty-six patients who had an initial diagnosis of dysplasia progressed from indeterminate to low-grade dysplasia [24.2 (11.0-30.4) months]. Low-grade dysplasia was associated with a 2% (1/56; T2N0M0) risk of CRC when present in random surveillance biopsies and a 3% (2/61; T1N0M0, T4N0M0) risk if detected in endoscopically visible lesions [7.4 (5.2-33.3) months]. Eighteen patients progressed from indeterminate to high-grade dysplasia [19.1 (9.2-133.9) months]. Seventeen patients progressed from low to high-grade dysplasia [11.0 (5.8-30.1) months]. None of the patients with high-grade dysplasia (0/35) progressed to CRC [4.5 (1.7-9.9) months]. CONCLUSION Dysplasia was associated with a low incidence of node negative CRC if surgery was deferred for up to 5 years. These findings may help inform the decision-making process for asymptomatic patients who are having to decide between intensive surveillance or surgery for UC-associated dysplasia.