Chronic neck pain is highly prevalent. To determine the efficacy and safety of acupuncture, in comparison with transcutaneous nerve stimulation-placebo (TENS-placebo) in the treatment of chronic uncomplicated neck pain, a single blind prospective study was designed, to be carried out at a Primary Healthcare Centre, with random assignment to two parallel groups and with evaluation and analysis by independent evaluators. A random assignment was made from 123 patients of the 149 initially recruited. These patients had been diagnosed with uncomplicated neck pain and experienced neck motion-related pain intensity equal to or exceeding 30 on a visual analogue scale (VAS) from 0 to 100 mm. The treatment with acupuncture was compared with TENS-placebo, applied over 5 sessions in three weeks. The primary endpoint was the change in maximum pain intensity related to motion of the neck, one week after the final treatment. Sensitivity was analysed per protocol (PP) and variant analyses were by intention to treat (ITT). Adjustment was made for confounders by multiple linear regression, including baseline values and rescue therapy. By ITT analysis, the change in the pain-VAS variable was greater among the experimental group (28.1 (95% CI 21.4-34.7)). The improvements in quality of life (physical aspect), active neck mobility and reduced rescue medication were clinically and statistically significant. In the treatment of the intensity of chronic neck pain, acupuncture is more effective than the placebo treatment and presents a safety profile making it suitable for routine use in clinical practice.