Until now, peripheral vascular endothelial function testing has been performed in research laboratories under highly controlled conditions, thus limiting its clinical applicability. In this study, we evaluated endothelial function in two peripheral vascular beds before and during reactive hyperemia in an outpatient clinic setting. The brachial artery was imaged with a portable ultrasound device and changes in vessel diameter were expressed as percent flow-mediated dilation (%FMD). Pulse wave amplitude of the finger was detected by peripheral arterial tonometry (PAT) and PAT hyperemia was defined as the maximal plethysmographic recording compared to baseline. Sixty individuals (43 men) were enrolled with an average age 53 +/- 2 years (mean +/- SE). The 31 individuals with more than two cardiac risk factors (CRF) had lower FMD (7.0 +/- 1.1%) and PAT hyperemia (2.1 +/- 0.9) compared to the 29 individuals with 0-2 CRF (FMD 11.3 +/- 0.8%, PAT hyperemia 2.4 +/- 0.1; p < 0.05 for both). The 32 individuals with coronary artery disease (CAD) had lower FMD (6.8 +/- 1.1%) and PAT hyperemia (2.0 +/- 0.1) compared to the 28 individuals without CAD (FMD 11.5 +/- 0.8%, PAT hyperemia 2.4 +/- 0.1; p < 0.05 for both). Thus, peripheral vascular endothelial function testing in the ambulatory setting correlates with the extent of CAD risk and the presence or absence of CAD. In conclusion, these data suggest that peripheral vascular endothelial function testing is feasible in ambulatory patients, and this is an important next step in bringing this technology to clinical applicability.