OBJECTIVE: To review potentially serious adverse events associated with acupuncture. QUALITY OF EVIDENCE: Studies in the medical literature primarily provide level II evidence from retrospective reviews, case reports, and prospective surveys of practitioners. MAIN MESSAGE: Both the general public and physicians are becoming more interested in the ancient Chinese medical practice of acupuncture. This paper discusses the basic philosophy of acupuncture and describes adverse events that might be associated with acupuncture treatment. Some events, such as nausea and syncope, can be mild and transient, but rare events, such as septicemia and hepatitis C infection, can be fatal. As the role of acupuncture in today's multidisciplinary clinics increases, the complications of acupuncture, although infrequent, cannot be overlooked. CONCLUSION: Responsible clinicians practising acupuncture and seeing patients who use acupuncture should be aware of the adverse events associated with it.