 There is limited data on the change in bone mineral density due to chemotherapy in postmenopausal women. This prospective study will gather data on the effects of systemic breast cancer therapy on bone mineral density in postmenopausal women receiving adjuvant care for early stage 0, I, II or III breast cancer. Postmenopausal women are the focus of this study because: 1 they are the largest subgroup of women with breast cancer 2 they are expected to have a rate of BMD loss unless disturbed by disease or medications, unlike the pre and perimenopausal women whose BMD is dramatically affected by changes in hormonal status 3 this group of patients is at greatest risk for acute osteoporotic fractures. 