Vancomycin is a glycopeptide antibiotic that is active against staphylococci, streptococci, and other gram-positive bacteria. It is the drug of choice for the treatment of infections due to methicillin-resistant staphylococci, Corynebacterium jeikeium, and multiply resistant strains of Streptococcus pneumoniae. Vancomycin is an alternative treatment for serious staphylococcal and streptococcal infections, including endocarditis, when allergy precludes the use of penicillins and cephalosporins. Vancomycin is bactericidal against most strains of staphylococci and nonenterococcal streptococci. Although rare strains of staphylococci and enterococci that are resistant to vancomycin have been reported, bacterial resistance has thus far not emerged as a major clinical problem despite widespread use of vancomycin. When therapy is monitored by periodic determinations of serum concentrations of the drug and rapid infusion rates are avoided, vancomycin is rarely associated with serious toxicity.