This is a longitudinal study to determine the influence of the menopause transition on autonomic and vascular function. PI Keller-Ross has published data demonstrating that postmenopausal females have greater sympathetic neural reactivity during a stressor compared with age-matched males and younger females and males. A paucity of literature exists, however, on the role of the menopause transition in autonomic function because the majority of experimental studies on menopause physiology are cross-sectional and/or focused on older, postmenopausal females . The influence of age on HTN is robust, whereas the effects of menopause are still unclear. Preliminary data demonstrate a clear association between age and sympathetic activity in females; how the transition through menopause influences these relations, however, remains unknown. The study will enroll 80 midlife (45-55 years of age) females to measure longitudinally the trajectory of autonomic and vascular function during the transition through menopause. The study hypothesizes that through the menopause transition, an increase in sympathetic activity and an impaired baroreflex sensitivity and endothelial function will emerge.