Abstract Women spend about one-third of their lifespan in the postmenopausal period. Menopause represents a vulnerable time in a woman's life for a number of reason, in particular, for her skeletal health. Estrogen deficiency associated with menopause increases bone remodeling leading to an imbalance between bone formation and bone resorption. The Study of Women's Health Across the Nation (SWAN) is an ongoing multicenter study designed to investigate a broad range physiological, psychosocial and social issues for women at midlife. The long range goal was to distinguish ovarian aging from chronological aging. Skeletal health was a particular focus of SWAN. At baseline, all 3302 women were age 42-52 years and pre- or early perimenopausal, having had a menstrual period within 3-months of study entry. A 10-year longitudinal analysis was conducted in a subset of 242 African American, 384 Caucasian, 117 Chinese and 119 Japanese women for whom a final menstrual period (FMP) could be defined. Bone loss was not evident during the pretransmenopausal state (between 5-years and 1-year prior to the FMP). Bone mineral density (BMD) loss began 1-year prior to FMP and slowed 2 years after FMP. Cumulative loss was greatest in Asian women and slowest in African American women. The 10-year cumulative loss of lumbar spine BMD was 10.6%, most of which was lost in the transmenopause period. This menopause associated estrogen deficiency might also influence breast density, a major risk factor for breast cancer. An ancillary study to SWAN focused on breast density: 1007 women from 3 sites were included. Mammograms that were taken 2-years before baseline up to 2-years after the 6th annual follow-up visit were retrospectively obtained and graded for breast density. Findings from the SWAN breast density include the observation that greater parity and younger age at first birth were inversely associated with breast density and may support a mechanism for parity and breast cancer through breast density. Smokers had lower breast density supporting an anti-estrogenic effect on breast tissue. The percentage of breast density decreased with increasing body mass index over time. In conclusion, the SWAN study provides important insights into menopausal health. Citation Format: Jane A. Cauley. Impact for the menopausal transition on skeletal and breast health. [abstract]. In: Proceedings of the Thirteenth Annual AACR International Conference on Frontiers in Cancer Prevention Research; 2014 Sep 27-Oct 1; New Orleans, LA. Philadelphia (PA): AACR; Can Prev Res 2015;8(10 Suppl): Abstract nr CN11-02.