There are no established risk factors for prostate cancer other than age, ethnic group, and family history. For dietary factors, the WCRF/AICR reported that diets high in vegetables were possibly protective, and that regular consumption of red meat, fat, saturated/animal fat, and milk and any products possibly increased risk. Among nutritional factors, a protective effect of lycopene, vitamin E, selenium, and perhaps fish oil and phytoestrogens appear particularly promising, although no definite answers have yet emerged. Although hormonal influences are biologically plausible, observational studies of androgen have not produced consistent results. While, insulin-like growth factor 1 could be a risk factor. Based on these evidences, several chemoprevention trials were launched using 5-alpha reductase inhibitor, selenium, vitamin E and so on.