With the widespread usage of acupuncture, the number of reports about complications of this treatment increases. Harmless disturbances are common and include minor bleedings or haematomas, pain during insertion or after withdrawal of the needle, and skin symptoms. In every second acupuncture treatment, at least one of these complications occurs. Orthostatic dysregulations are relatively rare and can be observed in only 1% of patients. They can be prevented by treating the patient in a lying position, especially in the first treatment session. Stab injuries of internal organs most often affect the lungs, resulting in a pneumothorax. At least 23 cases have been published, 2 of them with fatal consequences. An inquiry of Norwegian doctors even suggests that until 1995 in Norway alone 250 cases of pneumothorax after acupuncture occurred. Stab injuries of other internal organs or the CNS are only described in case reports, but some of them had fatal consequences. Stab injuries of peripheral nerves or large vessels and systemic bacterial infections like sepsis or endocarditis are very rare but serious consequences have been described. The transmission of viral infections due to insufficiently sterilised acupuncture needles loses more and more importance. The incidence of local infections can possibly be influenced, but even in Europe this complication still occurs frequently. The overview of published complications leads to the contraindications of acupuncture. Disturbances of coagulation, immune deficiency, abnormal heart valves or prosthetic valves are the most important ones to name. Suggestions for obtaining informed consent may be helpful while performing clinical trials., (Copyright 2001 S. Karger GmbH, Freiburg)