INTRODUCTION: Racial and ethnic differences in risk for cardiovascular morbidity and mortality are well documented. The relative role of genetic vs environmental influences is unclear. A non-invasive measure of autonomic balance, Heart Rate Variability (HRV) has been shown to be correlated with cardiovascular risk in some populations. Whether there are underlying differences in HRV between racial and/or ethnic groups, and whether this might therefore affect cardiovascular risk, is largely unknown. HYPOTHESIS: Young Asian males will have a higher HRV than matched Caucasians and will show a lower response to postural changes. METHODS: Subjects were in two groups; 1) Caucasian males aged 18 to 25 living all their life in Australia (n=20) and 2) age and BMI matched Asian males (“Asian” being defined as south east Asia, excluding the Indian sub-continent) resident in Australia (n=30). Subjects abstained from exercise, consuming alcohol, caffeine or guarana for 2 hours prior to the experiment. After 2 min acclimatisation, either standing or supine, the subject’s ECG was recorded for 15 min and HRV analysis conducted with AD Instruments (Australia) Chart 5/HRV module. The time domain measure used was SDdeltaNN, Frequency domain analysis used power spectral analysis to derive LF:HF ratio. RESULTS: There were no significant differences in age, BMI, hip:waist ratio or heart rate between the groups. There were no differences in blood pressure, except standing systolic blood pressure (137.2 ± 5.2 mm.Hg in Caucasian vs. 123.8 ± 2.8 mm.Hg in Asians; P<0.05). For both groups there was a significant decrease in SDdeltaNN and an increase in LF:HF ratio when standing compared to supine. Each of these changes was significantly larger for Caucasians compared to Asians for both measures (table 1). CONCLUSIONS: When moving from supine to standing, Asian subjects showed a lesser fall in HRV by both time domain and frequency domain measures compared to Caucasians. This appears to be because they have a larger reduction in vagal tone during this postural change. This may indicate a genetic difference between groups, and provide insight to the racial differences in risk for cardiovascular mortality and morbidity.