The effects of acupuncture on health are generally hard to assess. Stimulation of the P6 acupuncture point is used to obtain an antiemetic effect and this provides an excellent model to study the efficacy of acupuncture. Thirty-three controlled trials have been published worldwide in which the P6 acupuncture point was stimulated for treatment of nausea and/or vomiting associated with chemotherapy, pregnancy, or surgery. P6 acupuncture was equal or inferior to control in all four trials in which it was administered under anaesthesia; in 27 of the remaining 29 trials acupuncture was statistically superior. A second analysis was restricted to 12 high-quality randomized placebo-controlled trials in which P6 acupuncture point stimulation was not administered under anaesthesia. Eleven of these trials, involving nearly 2000 patients, showed an effect of P6. The reviewed papers showed consistent results across different investigators, different groups of patients, and different forms of acupuncture point stimulation. Except when administered under anaesthesia, P6 acupuncture point stimulation seems to be an effective antiemetic technique. Researchers are faced with a choice between deciding that acupuncture does have specific effects, and changing from 'Does acupuncture work?' to a set of more practical questions; or deciding that the evidence on P6 antiemesis does not provide sufficient proof, and specifying what would constitute acceptable evidence.