Abstract: Interference with formation of the complement-based membrane attack complex (MAC) will mitigate or even prevent tissue injury associated with the effects of complement in inflammation and graft rejection. Passive treatment of xenograft recipients at the time of and after transplantation with antibody against C-6, which interrupts the sequence of binding steps that form MAC, has been observed to suppress hyperacute xenograft rejection with no adverse signs or symptoms in the xenograft recipient. The present invention provides a method for interfering with MAC formation in transplant recipients, by administering compounds which interrupt one or more of the binding reactions between C5b and C6-C9, so that the MAC cannot form.