Objective: To detect early subclinical signs of autonomic dysfunction in the cardiovascular system and explore the mechanism of orthostatic hypotension (OH) in patients with multiple system atrophy (MSA). Methods: Eighteen male patients with possible MSA and 10 healthy men were recruited. The hemodynamic responses to head-up tilt and tilt-reversal were studied by an electrically-powered tilt table and a non-invasive cardiac output measurement (NICOM) system. Results: At supine, there was no signifi cant difference in blood pressure, heart rate (HR), stroke volume, cardiac output and total peripheral resistance between MSA patients and healthy controls. During tilting upright, OH developed in 5 MSA patients, with a 23.7±4.8 mmHg drop in systolic blood pressure. Patients with OH were older and exhibited higher scores in unifi ed Multiple System Atrophy Rating Scale part I than patients without OH. The stroke volume, cardiac output and total peripheral resistance did not differ between groups. The controls had the most signifi cant HR elevation (6.5±2.5 bpm) during tiltup, followed by patients without OH (2.8±1.6 bpm) and those with OH (-0.2±2.2 bpm). A similar trend of HR decrease was observed during return to supine posture. The process of tilt-reversal altered HR more signifi cantly than head-up tilt in controls (8.0±2.9 vs 6.5±2.5 bpm; P=0.031) and patients without OH (4.2±2.1 vs 2.8±1.6 bpm; P=0.032), but not in patients with OH (1.2±1.5 vs -0.2±2.2 bpm; P=0.380). Conclusions: The HR change during postural challenge showed signifi cant difference between MSA patients and healthy controls. Impaired HR responsiveness contributed to OH in MSA. Monitoring HR during the tilt table test may be a practical and useful method to detect early autonomic dysfunction in patients with MSA.