D uring the several-thousand-year history of which conditions and to what extent it is efacupuncture in Asia, a major apphcation fective, this has not been easily gained. Many has been the treatment of a broad range of pain complex problems have been confronted, not conditions. The modern era of acupuncture, the least of which has been the difficulty of concomprising the past two decades, has thor-ducting controlled clinical trials of acupuncoughly documented the safety and effective-ture. While researchers have attempted to folness of acupuncture analgesia for the treatment low a double-blind, placebo-controlled model of chronic and acute pain. Extensive clinical when testing acupuncture, this approach has and laboratory research has validated its use, raised numerous problems and has left many and detailed biomedical models have been pro-questions unanswered. Two of the difficulties posed to explain its action.immediately encountered were the virtual imAfter Nixon opened China to the West in possibility of blinding the acupuncturist (simi-1971, acupuncture became very popular as an lar to the problem of blinding a surgeon when alternative therapy for the treatment of pain testing a new procedure) and the uncertainties conditions. The international medical commu-inherent in choosing control acupuncture nity was startled, if not guardedly amazed by points. Inadequate solutions to these methodthe films of surgery on awake patients who ap-ological problems have often resulted in clinipeared to receive acupuncture analgesia in cal trials of questionable quality. Thus, when place of normal pharmaceutical anesthesia, reviewing an acupuncture efficacy trial with a This amazement was rapidly channeled into a reported negative outcome, it is critical to deconcerted research effort to understand how termine the extent to which the outcome was these surgical anesthesias were possible and due to poor study design rather than to an acthence to investigate the physiological mecha-tual failure of acupuncture to ameliorate the nisms by which acupuncture relieves pain, condition (see the paper of Lewith in this issue Many theories were put forward and tested, of the journal). Despite these considerable and many clinical trials were conducted to ex-problems, results indicating the efficacy of plore these questions. During the past 20 years acupuncture as an analgesic therapy have been or so, a growing database of clinical trials has found in a significant number of studies, for a produced a clear picture of how effective broad range of pain conditions. In this article, acupuncture can be for human and veterinary we discuss the following: treatment of a variety of pain conditions. Although the evidence has been building as to • Animal studies exploring mechanisms of achow acupuncture treats pain conditions and for tion of acupuncture as an analgesic therapy;