Tamoxifen is a candidate drug for prevention of breast cancer, although findings from trials have not been consistent. In our extended follow-up (median 81.2 months, IQR 66.0-87.2) of the Italian Tamoxifen Trial, this drug did not significantly protect against breast cancer in women at usual or slightly reduced risk of the disease (p=0.215). Use of hormone replacement therapy increased risk of breast cancer, and users of such treatment who were randomly allocated to tamoxifen had a rate of breast cancer that was close to that of never-users. So far, no woman has died from breast cancer in this study. Decisions about introduction of tamoxifen to reduce risk of breast cancer remain important and open questions.