Unlike the clinical setting, there is no published QC and assurance guideline specific to a toxicological pathology laboratory according to our literature search. As will become obvious in ensuing chapters, this is most likely because as in the case of any nonroutine test in a research setting, each antigen detection method requires its own in-built QC and assurance as a result of variations in available antibodies and the cell/ tissue types being studied for antigen localization. However, once the IHC method is established for a specific antigen, it is important that some type of QC procedure is in place to ensure consistent data. Therefore, based on the recommendations for QC and assurance in clinical IHC, we suggest that the “Total Test” approach be also considered as some form of QC for an IHC procedure in a toxicological pathology lab within a research setting since the same steps shown in Table 1.1 would be required for the IHC test. Along the same lines, the guideline for human tissues provided by the Canadian Association of Pathologists [12] is another one that could be adapted to suit toxicology needs and for rodents or other mammalian tissues since almost all the antibodies so far available for use in humans are also available and compatible for use in rodents.