Colorectal cancer is one of the most common malignancies and the most dreadful long-term complication in patients with ulcerative colitis. The incidence rate of colorectal cancer ranks second among the malignancies all over the world, and the number is still rising. Amid the many risk factors for colorectal cancer, ulcerative colitis is becoming increasingly prominent. The risk of colorectal cancer in ulcerative colitis patients is estimated to be as high as 40%. There is now a consensus that patients with long-lasting ulcerative colitis (﹥10 years) carries an increased risk of dysplasia and cancer. Taking into account evidence from the current studies, the longer ulcerative colitis lasts, the higher risk of colitis- associated colorectal cancer occurs. Unlike sporadic colorectal cancer, colitis-associated colorectal cancer usually derives from focal or multifocal dysplastic mucosa in areas of inflammation through an inflammation-dysplasia-carcinoma sequence. The prognosis of colorectal cancer is poorer in patients with ulcerative colitis than those without. Therefore the presence of dysplasia in ulcerative colitis patients is a critical indication of cancer that we should watch out for. Thus, early detection and resection of precursor lesions, mainly dysplasia, to terminate the cancerous progression is of great importance. To date, chemoprophylaxis, colonoscopy surveillance and proctocolectomy have been encouraged to prevent and manage dysplastic lesions in ulcerative colitis. This article attempts to give an overview of current research of dysplasia and prevention/management of dysplasia and colitis-associated colorectal cancer in ulcerative colitis.