Chemoprevention with food phytochemical is currently regarded as one of the noticeable scientific fields. A large body of data from epidemio‐logic and rodent studies has demonstrated that ingestion of vegetables and fruits is occasionally beneficial for reduction of cancer risks in humans. Recent clinical trials using ubiquitous antioxidants such as α‐carotene, however, have yet to show their cancer preventive effect despite the fact that they have been reported to be chemopreventive agents in rodent models. One of the goals of this review is to address useful and reliable methodology to detect promising chemopreventive agents from edible plants by highlighting molecular mechanisms of multistage carcinogenesis.