Establishment of preemptive medicine might be useful against the growing burden among colorectal cancer patients. Currently, we are trying to develop effective chemopreventive drugs not only for improving public health(i e, cancer morbidity and mortality), but also for better health economics and medical services. We have evaluated the suppressive effects of aspirin in subjects with a moderate-to-high risk of developing colorectal cancer through a randomized-controlled trial. For the first time, the efficacy of aspirin has been shown in Asian patients with adenomatous polyposis and recurrent colorectal tumors after endoscopic polypectomy. In this manuscript, we would like to show a good example of drug repositioning in cancer-preventive clinical trials and to discuss the future use of cancer-preventive agents.