Vancomycin is an effective and widely used antistaphylococcal antibiotic. Despite several decades of use, however, our knowledge of the toxicologic and pharmacokinetic properties of vancomycin remains incomplete. This review summarizes current information regarding the adverse reactions and pharmacokinetics of vancomycin. Although there have been reports of side effects with vancomycin, these effects tend to be infrequent, easily managed, and reversible. Several methods for adjustment of vancomycin therapy have been recommended. The relationship between serum concentrations of vancomycin and the occurrence of ototoxicity or nephrotoxicity has not been well established. However, because of large interpatient variations in pharmacokinetic parameters, it seems preferable to individualize vancomycin therapy based on serum concentration data.