The purpose of this study is to compare the efficacy of Faslodex (fulvestrant) to Aromasin (exemestane) in hormone receptor positive postmenopausal women with advanced breast cancer. Patients will be treated until disease progression or until the investigator has determined that treatment is not in the best interest of the patient, whichever occurs first.

Inclusion Criteria:

• Biopsy confirmation of Breast Cancer
• Breast Cancer has continued to grow after having received treatment with an aromatase inhibitor
• Postmenopausal women defined as a women who has stopped having menstrual periods
• Evidence of hormone sensitivity
• Written informed consent to participate in the trial

Exclusion Criteria:

• Previous treatment with Faslodex (fulvestrant) or Aromasin (exemestane)
• Any hormonal therapy used to modify the course of an additional medical condition after prior treatment with a non-steroidal aromatase inhibitor
• Treatment with an investigational or non-approved drug within one month
• An existing serious disease, illness, or condition that will prevent participation or compliance with study procedures
• A history of allergies to any active or inactive ingredients of Faslodex or Exemestane (i.e. castor oil or Mannitol)