Vancomycin, a useful bactericidal antibiotic for selective clinical infections, is the therapy of choice for serious staphylococcal infections when the penicillins and cephalosporins cannot be used. The antibacterial spectrum of vancomycin also covers other gram-positive cocci and bacteria and gram-negative cocci. Vancomycin is given intravenously in most cases, usually in a dose of 1 g every 12 hours in patients who have normal renal function. The indications for vancomycin therapy are as follows. 1. Serious staphylococcal infections in patients who are intolerant to the penicillins and cephalosporins or when the organism is resistant to the commonly used bactericidal agents. 2. Streptococcal endocarditis in patients intolerant to penicillin G; in enterococcal infections, it is used with an associated aminoglycoside. Vancomycin is not used alone in enterococcal endocarditis. In nonenterococcal (Streptococcus bovis) and viridans streptococcal endocarditis, vancomycin may be used alone if the minimum bactericidal concentration is less than or equal to 10 microgram/ml; otherwise, it is combined with an aminoglycoside. 3. Other serious infections caused by organisms resistant to the commonly used agents such as corynebacterial endocarditis. 4. Acute staphylococcal ileocolitis, for which vancomycin is given orally or orally and intravenously if indicated. Vancomycin is relatively nontoxic; the predominant toxic response is neurotoxicity, but this is rarely seen if the serum levels are 30 microgram/ml or less.