However, doctors are still debating whether this type of therapy has any effect beyond that of a placebo (a fake treatment with no real activity). It's a difficult question to resolve because most placebos are actually quite potent. Dummy pills typically achieve a relief rate of 30 to 35 percent, and a sham procedure, accompanied by suitably impressive instruments and rituals, can be effective more than 50 percent of the time. Indeed, in tests comparing genuine acupuncture with an imitation, patients receiving the fake treatment usually enjoy just about as much relief (50 percent) as those given the real thing.

Of course, if your only concern is pain relief (as opposed to a cure of the underlying problem), it doesn't really matter whether acupuncture's effects are physical or merely psychological, as long as you feel better. And there is, in any event, mounting proof of acupuncture's genuine value. According to an expert consensus panel convened by the National Institutes of Health (NIH) in 1997, well-performed scientific studies have provided evidence of acupuncture's efficacy in relieving pain after dental surgery and in reducing the nausea and vomiting associated with pregnancy ("morning sickness"), chemotherapy, and anesthesia. Other research suggests that acupuncture may be useful--along with other, more conventional therapies--for asthma, osteoarthritis, low back pain, headache (both tension and migraine), menstrual cramps, carpal tunnel syndrome, fibromyalgia, and other conditions that cause chronic pain.

Two other intriguing areas are currently under research. One is the use of acupuncture in easing withdrawal from addiction to hard drugs and alcohol; acupuncture, especially of the outer ear, is in use at many detoxification clinics in the United States. (Similar results have not been observed for tobacco addiction, however.) Another possibility is that acupuncture therapy may speed rehabilitation and limit damage after a paralyzing stroke.

The actual insertion of the hair-thin, disposable needles has been described as feeling like a mosquito bite. After insertion, the needles may be stimulated by twirling them or connecting them to a mild electrical current (there is no risk of electrical shock). This stimulation may cause a mild tingling or aching sensation referred to as "de qi." The needles may be inserted from a fraction of an inch up to about one inch deep. They can either be withdrawn a few seconds after insertion or kept in place for up to 30 minutes.

Treatment Time: Typically, you should allow 20 minutes to 1 hour per session. The initial visit may take longer.

Treatment Frequency: This varies according to the problem. You may start out with several treatments per week, then taper to weekly or less often. Duration of therapy may range from a few treatments for acute, temporary problems to regularly scheduled treatments over several months for chronic conditions.

How acupuncture works remains a mystery. According to ancient Chinese medical theory, the life force (called qi or ch'i and pronounced "chee") flows through the body via 14 invisible channels (called meridians), regulating all physical and mental processes. Opposing forces within the body, called yin and yang, must be balanced to keep ch'i flowing properly. The meridians supposedly run deep within the body's tissues and organs, surfacing at some 360 places identified as acupuncture points, sometimes called acupoints. Certain meridians are identified with organs such as the bladder or liver, and the points all along such meridians--even in the hands or feet--are believed capable of affecting the associated internal organ. Stimulating these points is said to balance and restore the flow of ch'i.

An explanation proposed by Western scientists is that acupuncture may trigger the release of natural pain-killing substances within the body called endorphins, thus blunting the perception of pain. It may also alter the body's output of neurotransmitters such as serotonin and norepinephrine, and of inflammation-causing substances such as prostaglandins. Like the manipulation of ch'i, however, this explanation has yet to be conclusively documented.

Whatever the cause may be, the pain-relieving effects of acupuncture seem to have a delayed onset; they increase slowly, even after removal of the needles, and may become more evident after several treatments. The effects may diminish after acupuncture treatments are ended.

Educational requirements for licensure vary by state, and this regulatory patchwork makes it difficult to judge an acupuncturist's credentials. Even the titles vary; an acupuncturist may be "licensed," "certified," or "registered," and in a few states may even have the title of "doctor" of acupuncture or Oriental Medicine. Just to make matters more confusing, these titles bear no consistent relationship to educational requirements, which range from 1,300 to 2,600 hours of training (usually in an accredited school or college of acupuncture). Surprisingly, the least qualified practitioners may be physicians, who are permitted to practice acupuncture with no training at all (although most have attended at least a few courses).

There are about 10,000 licensed, registered, or certified acupuncturists in the U.S., and an additional 3,000 medical doctors (MDs) or doctors of osteopathy (DOs) who practice the technique. To learn more about qualification standards and practitioners in your state, contact the groups listed under "Resources." Two of them may prove particularly helpful. The Accreditation Commission for Acupuncture and Oriental Medicine sets standards for acupuncture schools throughout the United States, and can send you a list of accredited schools. The National Certification Commission for Acupuncture and Oriental Medicine (NCCAOM) administers a standardized examination testing theoretical and practical knowledge of acupuncture. Those passing this test must meet continuing education requirements every two years in order to retain certification. There are currently 5,000 practitioners who have achieved certification, and an increasing number of states are using the examination as part of or acupuncture licensure. When choosing a therapist, you should check to see whether he graduated from an accredited school and whether he has received NCCAOM certification.

Unfortunately, no degree or license can reveal the most important variable: skill and talent. Before undergoing treatment, you may also wish to learn more about the practitioner's approach and philosophy. Some practitioners combine acupuncture with other aspects of traditional Chinese medicine, such as the use of traditional herbal remedies and the technique called moxibustion (applying a smoldering cone of herbal material to the skin at an acupuncture point). If your experience with one acupuncturist is negative, remember that it's possible for a different practitioner to produce better results.