A validated liquid chromatography tandem mass spectrometry (LC/MS/MS) method is presented for the analysis of per- and polyfluoroalkyl substances (PFAS) in serum and plasma. The method employs stableisotope labeled internal standard (IS) and surrogate recover standard (SRS) spiked serum or plasma samples that are mixed and precipitated with acetonitrile. Quantitation is performed with stable-isotope IS solvent (50 : 50 acetonitrile : water) calibration using one direct injection (DI) chromatographic analysis of precipitated sample supernate. The analytical method includes fifteen stable isotope labeled ISs, four SRSs ([1,2,3,4-C-13(4)]PFOA, [1,2-C-13(2)]PFUnA, [1,2,3,4-C-13(4)]PFOS, [2,3,4-C-13(3)]PFBA), and sixteen target analytes perfluoroalkyl carboxylic acids (PFCAs) (C4-C12), perfluoroalkyl sulfonic acids (PFSAs) (C4, C6, C8), N-ethyl perfluorooctane sulfonamido acetate (EtFOSAA), N-methyl perfluorooctane sulfonamido acetate (MeFOSAA), perfluorooctane sulfonamide (FOSA), and perfluorobutane sulfonamide (FBSA). Mean recoveries of control human plasma fortified with method target analytes over the range 2.5-175 ng mL(-1) (10-700 ng mL(-1) PFOS) are 83.7-103% with relative standard deviations (RSDs) of <= 14% (PFBA = 19%). Mean recoveries and RSDs of control human plasma fortified with mixed branched and linear isomer PFOA and PFHS (2.5 & 10.0 ng mL(-1)), and PFOS (10 & 40 ng mL(-1)) were 83.2% (RSD +/- 7.7%), 101% (RSD +/- 4.9%), and 101% (RSD +/- 6.5%) respectively. Mean recoveries of control bovine serum fortified with the method target analytes over the lower concentration range 0.250-175 ng mL(-1) (1-700 ng mL(-1) PFOS) are 82.8-103% with RSDs <= 15% (MeFOSAA = 16%, EtFOSAA = 17%). Mean recoveries and RSDs for 736 American Red Cross (ARC) study plasma samples fortified with SRSs at 1 ng mL(-1) were 89.0% (+/- 7.3% RSD) for [1,2,3,4-C-13(4)]PFOA, 91.8% (+/- 10% RSD) for [1,2-C-13(2)]PFUnA, and 89.4% (+/- 7.9% RSD) for [1,2,3,4-C-13(4)]PFOS.