Venous reflux in the internal jugular vein branches (JB) was found frequently in patients of certain neurologic disorders. We hypothesized that the retrograde-flow in JB is associated with retrograde hypertension transmitted from the internal jugular vein (IJV), which presumably underlies those neurologic disorders. In this study, we used color-Doppler imaging to evaluate the dynamic venous flow patterns in the IJV and its branches in 50 normal individuals (21 men, 29 women; mean age: 40.9 +/- 14.9 y, range: 22 to 70 y). The flow-direction of all detected JB (n = 100) was flowing into the IJV at baseline. During the Valsalva maneuver (VM), 38 JB (38%) had a retrograde-flow. Retrograde-flow in JB was significantly associated with IJV valve incompetence (OR = 7.6; 95% CI = 2.6 to 21.8; p = 0.0002) and greater IJV blood flow volume (blood flow volume >670 mL/min) (OR = 6.6; 95% CI = 1.8 to 24.5; p = 0.0052), both of which may reflect higher IJV pressure transmission during VM. The sonographic findings can be used in the future studies of diseases that are suspected to be related with retrograde cerebral venous hypertension due to an elevated IJV venous pressure.