3,3' Diaminobenzidine (DAB) Plus is a widely used chromogen for immunohistochemical staining and immunoblotting. In the presence of peroxidase enzyme, DAB produces a brown precipitate that is insoluble in alcohol. This product is available in a two component form consisting of a liquid, refrigerator stable DAB Chromogen Plus and DAB Substrate Plus. The standard working dilution is 20 μl of DAB Chromogen Plus per 1ml of DAB Substrate Plus, although the ratio can be adjusted as desired. The use of liquid components reduces some risks associated with the handling of powders (i.e. dust inhalation) and eliminates waste, which often results from using tablets that require a predetermined final volume. The two components must be mixed fresh for each use or immediately before an autostainer staining run. Remaining reagent should be discarded.