The objective of the present study was to obtain brachial artery (BA) baseline shear stress (SS) values in healthy volunteers and to relate this to gender and age. Peak and mean wall shear rate (SR) were noninvasively measured in 30 healthy subjects using an SR estimation system. Arterial diameter and wall characteristics were obtained with a wall tracking system. SS was estimated from SR and calculated whole blood viscosity. Intrasubject variability and the effects of age and gender were assessed. Intrasubject variability of BA peak and mean SR were 16.2% and 28.6%. Baseline peak ( approximately 3.0 +/- 0.7 Pa) and mean SS ( approximately 0.5 +/- 0.2 Pa) were not gender-dependent, nor were they influenced by age. No vessel wall parameter related to BA SS. No differences in BA SS were observed between the genders and no influence of age was apparent. Our results indicate that the BA adequately responds to chronic changes in blood flow.