A slender woman received acupuncture from a fully trained medical acupuncturist, including needling of the points LU 1 in the subacromial region and BL 13, which is a paravertebral point at the level of the spinous process of the third thoracic vertebra. During the final treatment, she experienced difficulties in breathing and pain in the left chest. On X-ray examination a tension pneumothorax was diagnosed, which, according to the authors of this report, was almost certainly caused by acupuncture.