A retrospective analysis was performed on 31 consecutive locally advanced or metastatic breast cancer patients who commenced exemestane 25mg/d orally following previous treatment with Tamoxifen and a non-steroidal third-generation aromatase inhibitor (AI). Patients were seen 3 monthly until clinical or radiological disease progression. Median age was 64 years (range 34-90 yrs). The average number of recurrences before starting exemestane was three (range 1-6). There were two complete responses (CR), four partial responses (PR), 12 with stable disease (SD) and 12 with progressive disease (PD). Objective response rate (CR+PR) was 19.4% and overall clinical benefit (CR+PR+SD >or= 24 weeks) was 54.8%. The median durations of objective response and overall clinical benefit were 18 and 14 months, respectively. This data support the anti-tumour activity of exemestane 25mg daily in patients with locally advanced and/or metastatic breast cancer who have been previously exposed to non-steroidal AIs and Tamoxifen.