Backgrounds: Abnormalities in flow-mediated-dilation (FMD) have been described in subjects with atherosclerosis and may be a marker of future cardiac events. The utility of FMD measure of endothelial function is limited by operator dependence. Pulse amplitude tonometry (PAT) is a novel, less operator-dependent technique to assess endothelial function. This study compares PAT to FMD in coronary artery disease (CAD). Methods: We performed measurements of a novel finger plethysmograph (Endo-PAT 2000) and compared the findings with a simultaneous noninvasive measurement of endothelial function with FMD using brachial artery in 80 subjects. The reactive hyperemia index (RHI) was defined as the ratio of pulse wave amplitude during reactive hyperemia relative to the baseline. Flow-mediateddilation (FMD) was defined as the ratio of the brachial artery diameter during reactive hyperemia relative to the baseline. The baseline characteristics, medications, cardiovascular risk factors were recorded. FMD and PAT were performed simultaneously. Results: Forty-six men and 34 women were examined. Average age was 62짹5 years. There was a linear relationship between the RHI and FMD during the same episode of reactive hyperemia (r = 0.45, P <0.001). Subjects in the lowest FMD quartile had the lowest PAT hyperemia ratio, whereas subjects in the highest FMD quartile had the highest PAT hyperemia ratio (P <0.01 for trend). Similar to FMD, the RHI was more impaired in subjects with cardiovascular risk factors and in subjects with severe coronary artery disease. Conclusion: Assessment of Endo-PAT demonstrates patterns of abnormality similar to that of FMD. These findings support the concept that analysis of Endo-PAT may be used to study peripheral vascular endothelial function.