Therapeutic drug monitoring (TDM) is specific method of clinical pharmacology for monitoring of the therapy using measurement of drug serum concentrations followed interpretation and good cooperation with clinician. TDM help clinicians to quickly optimize vancomycin dosing regimens to maximize the clinical effect and minimize the toxicity of the drugs. Minimum serum vancomycin trough concentrations should always be maintained above 10 mg/L to avoid development of resistance, neverthelles trough concentrations > 20 mg/L are not recommended because of the risk of nephrotoxicity. For serious infections vancomycin trough concentrations of 15-20 mg/L are recommended and for a pathogen with an MIC of 1 mg/L, the minimum trough concentration would have to be at least 15 mg/L to generate the target AUC24/MIC 400 (area under the curve/minimal inhibitory concentration). In non-complicated infections trough concentrations of 10-15 mg/L should be sufficient. For continuous infusions of vancomycin target steady-state concentration values of 15-25 mg/L have been advocated for critically ill patients.Key words: therapeutic monitoring - trough concentration - vancomycin.