The Endogenous Biotin-Blocking Kit provides a method and reagents for a pretreatment that reduces or eliminates background signals when biotin-avidin or biotin-streptavidin detection systems are used to identify cellular targets. The Endogenous Biotin-Blocking Kit offers: Improved results—increased signal-to-noise ratio facilitates cell target identification Ease of use—pipette-free dropper bottle offers speed and convenience Fast—endogenous background reduction in under an hour Flexibility—the kit can be used to help improve results from conventional immunohistochemistry, immunocytochemistry, RNA FISH, and ELISA procedures Biotin occurs naturally, functioning as an enzyme cofactor in the cytosol and mitochondria of a wide variety of cell types. The Endogenous Biotin-Blocking Kit minimizes interference from the endogenous biotin found in enzymes of mammalian cells and tissues, through a two-step blocking strategy. First, an excess of unlabeled streptavidin is added to the specimen to bind endogenous biotin-rich enzymes. The streptavidin is subsequently blocked with an excess of unlabeled biotin, effectively rendering the cell or tissue sample free of available biotin-binding sites.