Provided are methods for and compounds for modulating the complement system. In particular, compounds are provided that inhibit complement activation and compounds are provided that promote complement activation. The compounds are therapeutics by virtue of their effects on the complement system. Hence, the compounds that inhibit complement activation can be used for treatment of ischemic and reperfusion disorders, including myocardial infarction and stroke, sepsis, autoimmune diseases, inflammatory diseases and diseases with an inflammatory component, including Alzheimer's Disease and other neurodegenerative disorder.