Immunohistochemistry currently is the most powerful tool to identify specific molecules in situ. Moreover, antibodies can detect modifications of cellular polypeptides that occur naturally or as a result of toxic or other injuries. Here we report on a variety of parameters (fixation, tissue pretreatments, chromagen intensification, etc.) that we found to enhance immunohistochemical staining. Further, the use of well characterized antibodies and concomitant immunoblotting help avoid false positive results in immunohistochemistry. Finally, the sensitivity of the immunohistochemical procedure, regional differences in immunostaining within the central nervous system, as well as the recognition of equivalent molecules across different animal species are discussed.