The velocimetric complexes of vertebral arteries were studied following up 4 parameters of the frequency spectrum: peak of systolic velocity-PSV; end systolic velocity-ESV; mean diastolic velocity MDV; end diastolic velocity EDV. According to this study, it seems that MDV related to PSV is more indicated than EDV to appreciate cerebrovascular resistance. The increase of MDV related to the systolic velocity is more constant and ample from segment V1 to segment V3, compared with the increase of EDV. Thus, to appreciate circulatory resistance at downgrade, instead of Pourcelot value, there can be used the relation MDV/PSV or their difference related to PSV because MDV follows the variations PSV more exactly than EDV.