Colorectal cancer is one of the complications of ulcerative colitis (UC) and the risk of cancer increases as the duration of the disease becomes longer. Surveillance colonoscopy has been considered to be important for the early detection and early treatment of colorectal cancer, especially in longstanding UC. Because it is not always easy to detect neoplastic lesions in UC endoscopically, guidelines recommend the use of step biopsy in surveillance, in which either 4 biopsy specimens for every 10 cm or a total of 33 or more biopsy specimens are obtained. However, it has been pointed out that a step biopsy obtaining several tens of biopsy specimens may not be an ideal method in terms of invasiveness to the patient or medical cost. Instead of step biopsy, recent studies report the usefulness of target biopsy, in which biopsy tissues are obtained only from regions suspected of neoplasia. Therefore, the Research Group for Intractable Inflammatory Bowel Disease of the Ministry of Health, Labour and Welfare of Japan has initiated a randomized controlled study to compare the efficacy of step biopsy and target biopsy. The present article gives an introduction to this ongoing randomized controlled trial in Japan.