Antibiotic resistant bacteria are increasing worldwide. Multi-drug resistant streptococci (such as pneumococci) and staphylococci re now common. Some enterococcal strains have become resistant to all effective antimicrobial agents including vancomycin. Antibodies may be useful to prevent infections caused by resistant bacteria and may be useful as adjunctive treatment with antibiotics especially when organisms are resistant to antibiotics. Immunoglobulin can act at several sites to block bacterial invasion and eradicate infection. Antistreptococcal antibodies have been shown to promote phagocytosis and enhance clearance of bacteria from the blood. In addition, immunoglobulin can prevent neutrophil storage pool depletion and maintain circulating blood neutrophils. Staphylococci are becoming an increasing problem in nosocomial infection and opsonic antibodies may play an important role in immunity to both coagulate negative and positive staphylococcal infections. As bacteria become resistant to antibiotics, antibodies may become a critical part of our antimicrobial armamentarium.