Purpose: Abnormalities in pulse wave amplitude (PWA) have been described in subjects with atherosclerosis and may be a marker of future cardiac events. We evaluated the relationship between changes in PWA of the finger and peripheral endothelial function. Methods: We performed measurements of PWA with a novel finger plethysmograph (peripheral arterial tonometry, PAT) and compared the findings with a simultaneous noninvasive measurement of peripheral endothelial function with flow-mediated dilation (FMD) in 27 young healthy subjects (male 20 (74.1%), mean age 23.6  1.3 yrs). The PAT hyperemia ratio was defined as the ratio of PWA during reactive hyperemia relative to the baseline. FMD was defined as the ratio of the brachial artery diameter during reactive hyperemia relative to the baseline. Also, we evaluated the endothelium-independent responses by sublingual nitroglycerin (NTG) in both PAT (PAT-NTG) and FMD (FMD-NTG). Results: Subjects were not obese (body mass index 22.0  2.1 Kg/m2) and had no hypertension. There was a linear relationship between the PAT hyperemia ratio and FMD during the same episode of reactive hyperemia (r = 0.46, p = 0.020). Also, there was a positive correlation between the PAT-NTG and FMD-NTG during sublingual nitroglycerin (r = 0.50, p = 0.011). Conclusions: Assessment of PWA with PAT demonstrates patterns of abnormality similar to that of FMD. These findings support the concept that analysis of PWA with PAT during reactive hyperemia may be used to study peripheral vascular endothelial function.