Study summary: The present prospective study was designed to evaluate the association between meat, meat-cooking methods, and meat-mutagen intake and postmenopausal breast cancer in the NIH-AARP Diet and Health Study cohort. A number of studies have found an association between breast cancer risk and intake of red meat or meat cooked at high temperatures, but other studies have found no association. The study included 120,755 postmenopausal women who completed a food questionnaire during 1995-1996 and a detailed meat-cooking survey within six months following baseline. During eight years of follow-up, 3,818 new cases of breast cancer were identified in this study group. After adjusting for covariates, no associations with breast cancer risk were found for consumption of overall total meat, red meat, meat cooked at high temperatures, and meat mutagens. The authors conclude that this major study, which included detailed information on meat preparation methods, provides no support for a role of meat mutagens in the development of postmenopausal breast cancer.