BackgroundMen and women differ in the risk of cardiovascular disease, but the underlying mechanisms are not completely understood. We examined possible sex‐related differences in supine and upright cardiovascular regulation. Methods and ResultsHemodynamics were recorded from 167 men and 167 women of matching age (≈45 years) and body mass index (≈26.5) during passive head‐up tilt. None had diabetes mellitus or cardiovascular disease other than hypertension or used antihypertensive medication. Whole‐body impedance cardiography, tonometric radial blood pressure, and heart rate variability were analyzed. Results were adjusted for height, smoking, alcohol intake, mean arterial pressure, plasma lipids, and glucose. Supine hemodynamic differences were minor: Men had lower heart rate (−4%) and higher stroke index (+7.5%) than women (P55 years). Heart rate variability analyses showed higher low:high frequency ratios in supine (P