According to an article in today's US NEWS & WORLD REPORT, Western science is beginning to understand (at least in terms they can understand) how acupuncture works. The story is actually about a study coming out in the September issue of NeuroImage where positron emission tomography scans of the brain showed changes caused by acupuncture.
This latest study showed that acupuncture increases the binding availability of mu-opioid receptors in regions of the brain that process and weaken pain signal, in other words it reduces pain. Western medicine continues to try and squeeze that square peg of acupuncture into their round hole of science to try and understand how it works. The fact that it's been used by billions of people for 5,000 years doesn't carry any weight with Western medicine.
They're slowing coming along and accepting that acupuncture does work. Better late than never.