Summary: In January of 1999 the Belgian food supply was contaminated with transformer fluids containingpolychlorinated biphenyls (PCBs). The Belgian government public health response to this contamination incident was detailed by G. De Poorter at the 19th International Symposium of Halogenated Environmental Organic Pollutants (Dioxins 99) in Venice, Italy on September 17, 1999. The source of contamination was a storage tank at the Verkest fat-rendering works. PCB transformer oil was included in fat that was being recycled for a feed additive in composite feed. The transformer oil contained predominantly Aroclor 1254 and 1260 that was contaminated with traces of chlorinated dibenzofurans (PCDFs) and chlorinated dibenzo-p-dioxins (PCDDs). The contamination incident was highlighted by a sudden drop in egg production, reduced egg hatchability and increased mortality of chicks. The Belgian government mobilized a major public health effort aimed at: a) identifying the contaminated feed materials; b) placing quarantine on those farms that were identified as being contaminated with PCBs; c) undertaking a major analytical effort to identify the extent of the contamination; d) isolating and destroying animals determined to be contaminated. The extent of this public health disaster resulted in a commitment from the Bclgian government that a system would be identified to prevent a reoccurrence of contamination of the food supply with these toxic environmental contaminants. The Belgian Ministries of Public Health and Agriculture made a public tender for proposals for a screening methodology that would allow for the detection of contamination of fat, feed stuffs, animal fat, milk products, egg products and processed feed stuffs at the level of 5 pg TEQ/g fat. The competition involved the analysis of 23 samples for contamination on a TEQ basis of PCBs, and PCDDs/PCDFs. If possible, an analysis of the contribution of TEQ by the PCBs versus PCDDs/PCDFs was requested. Described in this report are the results of the CALUXTM analysis, as developed by Xenobiotic Detection Systems Inc., versus detection using gas chromatography/high resolution mass spectrometry (GC-HRMS) provided by various laboratories contracted by the Belgian government.