A review of the epidemiological and experimental data suggests that dietary modification does have a place in breast cancer prevention. This needs to be considered at three levels: dietary recommendations for the general population, dietary intervention in the management of women at high risk for breast cancer, and the place for dietary therapy as a component of regimens intended to reduce risk of recurrence after primary treatment of breast cancer ('secondary prevention'). Based on present evidence, a dietary approach to breast cancer prevention should include weight control, when indicated, a reduction in dietary fat intake to approximately 20% of total fats, and an increase in fiber consumption to 25-30 g day-1. Further studies are indicated to determine the optimal qualitative composition of dietary fat consumed, and the nature of supplemental fiber.