Metallothionein (MT) proteins are encoded by a family of genes containing at least 10 functional isoforms. Computational structural analysis has helped to better understand the structure of this protein. The MT protein is easily demonstrated by immunohistochemistry and immunoelectron microscopy. The advantage of immunohistochemistry is that it allows cellular localization of the proteins in fresh paraffin-embedded and archived specimens. MT proteins detected by immunohistochemistry can also be correlated with histopathological features of the tissue sections. There have been several reports on the immunohistochemical detection of the MT protein in a variety of tumors. However, as immunohistochemical methods are unable to distinguish the different MT isoforms, reverse transcription-polymerase chain reaction (RT-PCR) and in situ hybridization of mRNA transcripts have enabled the analyses of all known functional MT isoforms. Molecular biology techniques could therefore complement immunohistochemistry in the analysis of MT expression from transcription to translation.