The principle aim of the present work is the evaluation of the importance of the variable "depth" of needle insertion in the determination of acupuncture's therapeutic results. A randomized clinical trial carried out on 44 patients belonging to two groups of 22 each, suffering from shoulder myofascial pain: group A: superficial acupuncture; group B: deep acupuncture. All of them subjected to the same model of treatment with 13 needles and the treatment of the most painful 4 trigger points (TP) found in the shoulder's area. In the group A patients, the needles were introduced in the skin at a depth of 2 mm, on the TP. In the group B patients, the needles were placed deeply both in the muscular acupuncture points and in the TP. The treatment was planned for a cycle of 8 sessions, the first 4 to be performed twice a week, the last 4 weekly. The intensity of pain was evaluated with the McGill Pain Questionnaire before beginning the therapy, at the end of the therapy, and at the follow-up after 1 and 3 months. Both techniques had efficacy in controlling pain. A statistically significant difference rose between the two needling techniques at the end of the treatment and at the follow up after one and three months. Deep acupuncture shows to be better at all times and this underlines the importance of the muscular afferences in acupunctural stimulation in the control of pain.