Affinity-purified anti-horseradish peroxidase (HRP) may be used to detect HRP or to enhance signal by binding to HRP-conjugated molecules (such as HRP-conjugated antibodies or HRP-conjugated streptavidin) or HRP-containing complexes (such as PAP or HRP-ABC). Anti-HRP also may be used to convert an HRP conjugate into a different signal. 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 in animal tissues. Endogenous enzyme activity, typically detected with DAB, was not detected by anti-HRP (a plant enzyme). The procedure may also be used with fluorophore- or alkaline phosphatase-conjugated anti-HRP to amplify and/or convert signals as shown in the examples below.