Polybrominated diphenyl ether (PBDE) congeners and components of the complex mixture toxaphene are stable in the environment and readily bioaccumulated into wildlife and human tissues. PBDEs are presently used in large quantities worldwide as flame retardants in textiles, furniture, computer equipment, and cables. Toxaphene is a complex mixture of chlorinated bornanes and bornenes that was the most heavily used pesticide in the United States until it was banned in 1982; however, some countries continue to use toxaphene. The National Institute of Standards and Technology has quantified PBDE congeners and toxaphene in several available Standard Reference Materials (SRMs) using methods of gas chromatography with electron impact mass spectrometry (GC-EI-MS) and GC negative chemical ionization (NCI) MS, respectively. SRM1588a Organics in Cod Liver Oil and SRM1945 Organics in Whale Blubber were examined for PBDE congeners47, 99, 100, 153, and 154, total toxaphene, and toxaphene congeners26, 50, and 62. SRM 1946 Lake Superior Fish Tissue was also examined for total toxaphene and toxaphene congeners. The sum of the PBDE congeners (mean, (1SD) wet basis) for SRM1945 was 150ngg1 (7ngg1). The concentration of PBDE47 in SRM1588a was 82.7ngg1 (2.8ngg1). Other PBDEs were detected in SRM1588a but were not quantified due their low levels. The total toxaphene (wet mass basis) was 1,210ngg1 (127ngg1), 1,960ngg1 (133ngg1), and 3,980ngg1 (248ngg1) in SRMs1945, 1946, and 1588a, respectively. The values for PBDEs and toxaphene determined in the SRMs, while not certified, indicate that the SRMs will be suitable control materials for PBDE and toxaphene analyses.