The benefits of breast self-examination (BSE) for reducing mortality from breast cancer are uncertain. We conducted an analysis of the relationship between self-reported practicing of BSE and mortality from breast cancer over 13 years in a cohort of over 548,000 women. The report of practicing BSE was unrelated to breast cancer mortality. There was a small beneficial effect in those women who were the thinnest, but this effect was small and not statistically significant. BSE was otherwise equally ineffective in subgroups defined by obesity level and family history of breast cancer. We conclude that BSE, as practiced by American women in 1959, did not reduce the risk of mortality from breast cancer.