In this overview we emphasize new methods of improving immunohistochem
ical results in formaldehyde-fixed tissue samples. The benefit of heat
-induced antigen retrieval in demasking of concealed epitopes is demon
strated. We provide guidance on the influence of heat-induced antigen
retrieval in commonly applied monoclonal and polyconal antibodies. Mor
eover, we show the promising methods of signal amplification using bio
tinylated tyramine and signal intensification of diaminobenzidine reac
tion products by metallic ions.