Recent results from controlled trials of adjuvant tamoxifen and oophorectomy in early breast cancer are reviewed. The results of the statistical overview performed by the Early Breast Cancer Trialists Collaborative Group are summarised, and some important questions left open by this overview are discussed. These include the choice of patients for adjuvant endocrine treatment, long term results of tamoxifen, interaction with postoperative radiotherapy, the effect of tamoxifen on non-cancer deaths, and interaction of the adjuvant effect of tamoxifen with concentrations of oestrogen receptor levels in the tumour.