Abstract Body: INTRODUCTION: Nearly 75% of women experience vasomotor symptoms (VMS, e.g., hot flashes, cold flashes, and night sweats) during menopause. VMS are associated with lower endothelial function, a non-traditional risk factor for cardiovascular disease, in late perimenopausal and postmenopausal women. However, this association remains unexplored in women prior to or in the early stages of the menopause transition, such as late premenopausal (PRE) or early perimenopausal (PERI) women. HYPOTHESIS: Thus, the purpose of this cross-sectional study was to test the hypothesis that late PRE and early PERI women with greater severity and frequency of VMS have lower endothelial function. METHODS: Thirty late PRE and early PERI women (ages 41-55 years) were classified using the STRAW+10 criteria. Late PRE are in the final phase of reproductive years prior to the start of the menopause transition and characterized by regular menstrual cycles. Early PERI women are in the early phases of the menopause transition and characterized by frequent menstrual cycle irregularities. Severity and frequency of hot and cold flashes and night sweats were assessed with a 10-point Likert questionnaire, wherein higher scores indicate greater symptom burden (score range 0-30). Total scores were dichotomized by the sample median to generate a “Low Symptoms” (LS, score<7, n=14) and a “High Symptoms” (HS, score≥7, n=16) group. Endothelial function was assessed using brachial artery flow mediated dilation (FMD). Group differences were tested using unpaired t-tests. RESULTS: There were no significant differences in age (LS: 47±3 vs. HS: 48±3 years; p=0.33), body mass index (LS: 25.1±3.1 vs. HS: 25.8±3.8 kg/m2; p=0.58), systolic blood pressure (LS: 114±8 vs HS: 118±10 mmHg; p=0.25), or diastolic blood pressure (LS: 69±7 vs. HS: 71±7 mmHg; p=0.51). However, FMD tended to be lower in the HS group (LS: 6.64%±2.0; HS: 5.23%±2.20; p=0.08). CONCLUSION: These preliminary findings suggest that late PRE and early PERI women with greater VMS symptom burden may have reduced endothelial function. Additional research is needed to further assess this relation and the underlying mechanisms of VMS.