Third-generation aromatase inhibitors are accepted widely as alternatives to tamoxifen for the treatment of advanced breast cancer in postmenopausal women and, currently, are increasingly replacing tamoxifen in the adjuvant setting. This drug profile focuses on recent clinical developments in the use of anastrozole and, in particular, on the Arimidex, Tamoxifen, Alone or in Combination trial, which has shown that initial adjuvant treatment with anastrozole has significant efficacy and tolerability advantages compared with tamoxifen for postmenopausal women with early breast cancer. Results of adjuvant switching, extended adjuvant and preoperative (neoadjuvant) studies are reviewed and the potential of anastrozole in a range of clinical settings is discussed. Treatment recommendations and the future role of anastrozole in the management of patients with early breast cancer are also considered.