Recently, intra-Muscular Stimulation (IMS) therapy is being increasingly used for musculoskeletal pain. This procedure is generally regarded as a safe procedure in the general public. Some cases of iatrogenic pneumothorax caused by acupuncture have been reported in the medical literatures. However, IMS therapy associated pneumothorax has not reported. We experienced two cases of iatrogenic pneumothorax after IMS therapy. A 62 year-old man who had received IMS therapy on the right shoulder because of post neck pain. After IMS therapy, acute dyspnea and chest discomfort were developed. The other patient was 74 year-old woman who also received IMS therapy. She experienced nonproductive cough and acute dyspnea after the treatment. As the popularity of this form of alternative medicine increases, we might expect to see more cases. Physicians should be aware of the adverse events associated with IMS therapy.