There is a large and expanding body of scientific evidence supporting the use of acupuncture for pain control. The currently understood mechanisms of acupuncture analgesia are complex and involve direct and indirect neurohumoral effects that block pain perception, reduce the pain response, relieve muscle spasms and reduce inflammation. The analgesic mechanisms of electro-acupuncture (EA) involve the spinal cord grey matter, hypothalamic-pituitary axis, midbrain periaqueductal grey matter, medulla oblongata, limbic system, cerebral cortex and the autonomic nervous system. EA stimulation of these sites results in activation of descending pathways that inhibit pain through endogenous opioid, noradrenergic and serotonergic systems. Bilateral EA using mixed frequencies (low frequency of 2-20 Hz for a period followed by a high frequency of 100-200 Hz) will stimulate all endogenous analgesic systems and provide the best short and long term pain control. There are growing numbers of human trials supporting the use of acupuncture as an evidence-based practice for pain control which include: low back pain, neck pain, chronic idiopathic/migraine headaches, knee pain, shoulder pain, fibromyalgia, temporomandibular joint pain, postoperative pain. While the number of well-designed, controlled clinical research studies in veterinary medicine is lagging that of human medicine, much of the basic science research has been done in animals with neurophysiology more similar to veterinary patients than to humans. Although there is research to support EA as an evidence-based practice for the control of back pain in horses, further studies are needed in other clinical situations in veterinary medicine where analgesia is required.