Genistein, a major component of soybean isoflavone, has been shown to inhibit cell proliferation and enhance apoptosis in cancer cells. Accumulating bodies of evidence suggest that genistein is expected to synergistically promote the anti-proliferative effects of chemotherapeutic agents on neoplasia without toxicity. At molecular biological levels, a wide array of genistein targets has been characterized so far. These include transcription factors such as NF-kappaB and several signaling pathways. Genistein also reduces oxidative stress. When all the information is taken together, genistein could be applied together with chemotherapeutic agents to cure neurodegenerative disease as well as neoplasia. In this review, recent findings, of molecular actions of genistein, especially during the past three years, have been summarized to explore the potential therapeutic usage of genistein for human disease.