An Exercise Intervention for Breast Cancer Patients: Feasibility and Effectiveness (BEAT Cancer Trial; Pilot Study)

Inclusion Criteria: * Female breast cancer patients between the ages of 18 and 70 years of age with a diagnosis of Stage I, II, or IIIA breast cancer who are currently taking aromatase inhibitors or selective estrogen receptor modulators for the next 8 months. * English speaking * Medical clearance for participation provided by primary care physicians * If the patient has undergone a surgical procedure, must be at least 6 weeks post-procedure Exclusion Criteria: * Diagnosis of dementia or organic brain syndrome * Medical, psychological or social characteristic that would interfere with ability to fully participate in program activities and assessments (e.g., psychosis, schizophrenia, etc.) * Contraindication to participation in a regular physical activity program. * Metastatic or recurrent disease * Inability to ambulate * Engaged in \>/= 60 minutes of vigorous physical activity or \>/= 150 minutes of moderate plus vigorous physical activity per week during the past month.