The immunosuppressant everolimus was recently approved for prophylactic use in the United States, to prevent organ rejection in adult kidney transplant recipients. The currently accepted therapeutic range for everolimus is 3-8 ng/mL. Therapeutic drug monitoring (TDM) using predose EDTA whole blood samples is required to optimize dose. We describe a simple extraction method and analysis by liquid chromatography tandem mass spectrometry (LC-MS/MS) to support routine TDM of everolimus. Samples were prepared by protein precipitation and filtration. The first quadrupole was set to select the ammonium adducts (Equation is included in full-text article.)of everolimus (m/z 975.62) and rapamycin-d3 (m/z 934.70), the internal standard. The second quadrupole was used as a collision chamber, and the third quadrupole was then used to select characteristic product ions of everolimus (m/z 908.50 and 890.50) and rapamycin-d3 (m/z 864.60 and 846.50). The method had an analytical measurement range of 2.0-150 ng/mL. Total imprecision, expressed as percent coefficient of variation (mean concentration), was 19.1% (3.3 ng/mL), 10.6% (5.9 ng/mL), 8.1% (19.2 ng/mL), 5.7% (25.8 ng/mL), and 9.1% (34.2 ng/mL). The new method was compared with 2 other everolimus methods also based on LC-MS/MS, with 64 residual patient specimens. Agreement, based on simple linear regression, was excellent. Method A comparison: y = 0.96x - 1.12 (r = 0.99), n = 20, 2.5-44.7 ng/mL. Method B comparison: y = 0.96x + 0.49 (r = 0.99), n = 44, 2.1-85.6 ng/mL. We conclude that this method could support TDM of everolimus for a wide range of clinical indications.