Major advancements in the field of in situ molecular pathology have occurred since publication of the first edition. In Situ Molecular Pathology and Co-expression Analyses, Second Edition, continues to teach both the molecular basis for the improvements and the actual protocols. This is the unique feature that separates it from the pack of other “cook-book” type approaches. The fields of in situ hybridization and immunohistochemistry have expanded rapidly where computer-based analyses systems have greatly expanded the power of these methods. Further, knowledge of the marked improvements in the reagents themselves since the first edition can make the difference of excellent versus misleading data. The automated platforms require that researchers and diagnostic biomedical investigators have a good understanding of the basics of in situ based tests, protocols, and biochemistry for troubleshooting in order to maximize the use of these platforms. This second edition focuses attention on straightforward protocols used to simultaneously detect two or more proteins/nucleic acids within intact tissue by doing co-expression analyses. Practicing molecular pathologists, diagnostic pathologists, laboratory directors, and toxicologists, as well as clinicians and researchers in training, will benefit from this clear presentation of protocols and theoretical framework. Data derived from in situ hybridization and immunohistochemistry.