After reviewing more than 1,500 clinical charts of patients who received vancomycin therapy and whose serum vancomycin level was monitored, we identified 101 patients who also had the left ventricular ejection fraction (LVEF) assessed at that time. The fluorescence polarization immunoassay method was used to measure vancomycin serum concentrations in these patients 1 h after the end of vancomycin infusion and just before the next administration. Using these two measurements, we calculated the pharmacokinetic parameters using the Bayesian estimator