Objective: To verify the classic saying of "Treating lumbar-back problems by puncturing Weizhong(BL 40)" in acu-moxibustion learning and to explore its underlying mechanism.Methods: Forty volunteer subjects were asked to accept twice tests respectively

i.e.

acupuncture of Weizhong(BL 40) and Yanglingquan(GB 34)

for observing changes of skin blood perfusion(SBP) at the low back part of the body by using a laser Doppler perfusion imager.The whole observed area(lower back) was divided into five sub-areas

left and right areas involving Line-one and Line-two of the Bladder Meridian.Results: In comparison with pre-acupuncture

SBP of both BL40 and GB34 groups increased significantly from 4 minutes' retention of needles on to 12 min after withdrawing acupuncture needle(P<0.01)

but no significant difference was found between two groups in SBP(P>0.05).The change rates of SBP at Line-one and Line-two of the Bladder Meridian on the same side of the stimulated Weizhong(BL 40) were significantly higher than those of Yanglingquan(GB 34)(P<0.05)

but no significant changes were found on the opposite side(both Line-one and Line-two) of the Bladder Meridian.Conclusion: Acupuncture of both BL40 and GB34 can increase SBP at the low back of the body(involving the Bladder Meridian) on the same side

but the changing rate of SBP of BL40 is higher than that of GB34.