Acupuncture and moxibustion are safe treatments if implemented by trained, regulated practitioners with knowledge of human anatomy and potential adverse effects. Major (life-threatening) adverse effects are quite rare. They include pneumothorax, major hemorrhage, infection, septicemia, perforation of the brain stem, spread of blood-borne infections (such as hepatitis and human immunodeficiency virus), vascular damage, perichondritis, organ perforation, cardiac tamponade, bacterial endocarditis, arrhythmias, burns, scarring and allergic reactions. Instant recognition of these complications is required for successful emergent treatment, which may be life-saving. Minor adverse effects include mild skin reactions, dermatitis, local pain, bruising, syncope, and drowsiness. These are usually not problematic unless allowed to cause complications, such as trauma from syncope. Thorough history taking and attention to high practice standards will reduce the complication rate. This chapter covers well-documented adverse effects of acupuncture and provides guidance to avoid complications. In addition, it suggests guidelines for suspecting and dealing with acute emergencies. Cancer patients can be more susceptible to complications such as infection and bleeding. Moxibustion will also be examined, since it is often used as an integral part of cancer treatment in the East. It is important that the acupuncturist works closely with the oncologist to ensure appropriate application of acupuncture/moxibustion and to reduce the incidence of complications and ensure their timely management when they do occur. Risk factors for complications include: inadequate training, bleeding disorders, immunocompromised state, asthma, cachexia, diabetes, open wounds, cardic valve abnormalities and vasovagal sensitivity. There is evidence that increased training and awareness of potential adverse effects will reduce the incidence of adverse effects. Informed patient consent is important. Hospital and clinic practice guidelines and certification of staff will ensure that practice is as safe as possible.