The aim of this study is to test whether Arimidex alone or in combination with Tamoxifen is beneficial in the treatment of breast cancer.

Inclusion Criteria:

• Patients with histologically proven operable invasive breast cancer
• Patients who have completed all primary surgery and chemotherapy (if given), and are candidates to receive hormonal adjuvant therapy
• Women defined as post-menopausal

Exclusion Criteria:

• Patients in whom there is any clinical evidence of metastatic disease
• Patients who, for whatever reason (e.g. confusion, infirmity, alcoholism), are unlikely to comply with trial requirements
• Patients whose chemotherapy was started more than 8 weeks (ie 56 days) after completion of primary surgery or whose chemotherapy was completed more than 8 weeks (ie 56 days) before starting randomised treatment