On 21 September 2001 the Harvard Center for Cancer Prevention and the Cancer Epidemiology Program of the Dana-Farber/Harvard Cancer Center co-sponsored a symposium on diet and breast cancer for members of the Harvard breast cancer research community in Boston, MA. The purpose of the symposium was to review past findings and recent research developments in diet and breast cancer, and to potentially identify new opportunities for study. Presentations addressed research on the associations between phytoestrogens, total dietary fat, types of fat, olive oil, alcohol, folate/folic acid, and intakes of fruits and vegetables, and breast cancer risk. The relations between metabolic factors such as body mass index, weight gain, and breast cancer risk were also highlighted.