The Certificate of Analysis for SRM 1589a PCBs, Pesticides, PBDEs, and Dioxins/Furans in Human Serum has been updated to include certified concentration values for 27 polychlorinated biphenyl (PCB) congeners, three chlorinated pesticides, and four polybrominated diphenyl ether (PBDE) congeners as well as reference concentration values for 27 additional PCB congeners, six additional chlorinated pesticides, three additional PBDE congeners, and selected polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs). This represents an addition of concentration values for 29 PCB congeners and for PBDE congeners that were not quantified in the previous issue of SRM 1589a. With the increased number of certified and reference concentration values for PCBs and the inclusion of certified and reference concentration values for PBDEs, this serum material will be more useful as a reference material for contaminant monitoring in human tissues and fluids.