During the last 30 years, auricular acupuncture has been used as complementary treatment of cancer pain when analgesic drugs do not suffice. The purpose of this study is to examine the efficacy of auricular acupuncture in decreasing pain intensity in cancer patients. Patients and Methods: Ninety patients were randomly divided in three groups; one group received two courses of auricular acupuncture at points where an electrodermal signal had been detected, and two placebo groups received auricular acupuncture at points with no electrodermal signal (placebo points) and one with auricular seeds fixed at placebo points. Patients had to be in pain, attaining a visual analog score (VAS) of 30 mm or more after having received analgesic treatment adapted to both intensity and type of pain, for at least 1 month of therapy. Treatment efficacy was based on the absolute decrease in pain intensity measured 2 months after randomization using the VAS. Results: The main outcome was pain assessed at 2 months, with the assessment at 1 month carried over to 2 months for the eight patients who interrupted treatment after 1 month. For three patients, no data were available because they withdrew from the study during the first month. Pain intensity decreased by 36% at 2 months from baseline in the group receiving acupuncture; there was little change for patients receiving placebo (2%). The difference between groups was statistically significant (P < .0001). Conclusion: The observed reduction in pain intensity measured on the VAS represents a clear benefit from auricular acupuncture for these cancer patients who are in pain, despite stable analgesic treatment.