Although monitoring serum vancomycin concentrations in clinical practice is commonplace, the data supporting this practice are meager. The rationale for monitoring these concentrations is to improve the effectiveness and/or reduce the toxicity of the drug. However, there are no data to suggest that monitoring serum vancomycin concentrations improves the effectiveness of therapy. In addition, despite many case reports of vancomycin-associated nephrotoxicity and ototoxicity, it is unclear whether this agent truly causes such conditions. Moreover, there is no evidence that adherence to specific ranges of vancomycin concentrations will preclude these events. Finally, vancomycin pharmacokinetics are sufficiently predictable that adequate serum drug concentrations can be obtained with dosing methods that take into account the patient's age, weight, and renal function. Safe and effective vancomycin dosage regimens can be constructed with these empirical dosing methods, whereas monitoring vancomycin levels increases the cost of therapy without improving the safety or efficacy of treatment.