Whole molecules of affinity-purified anti-horseradish peroxidase (HRP) may be used to detect horseradish peroxidase or to enhance signal by binding to any HRP-conjugated molecule (such as HRP-conjugated secondary antibodies or HRP-conjugated streptavidin) or any HRP-containing complex (such as PAP or HRP-ABC). For example, our anti-HRP complexed with colloidal gold particles has been used with silver enhancement in place of diaminobenzidine (DAB) to create less diffused images following labeling of tissue sections with HRP reagents (Gee et al., J. Histochem. Cytochem. 1991. 39, 863; Roth et al., Methods in Lab. Invest. 1992. 67, 263; and Roth et al., Histochemistry. 1992. 98, 229). A further advantage of the technique was a reduction in background staining from endogenous peroxidase-like enzyme activity. The interfering endogenous enzyme activity, typically detected with DAB, was not detected by an antibody against HRP (a plant enzyme). The procedure may also be used with fluorophore- or alkaline phosphatase-conjugated anti-HRP to amplify signals as shown in the example below.