The Human Epidermal Growth Factor (HER-2) oncogene encodes a transmembrane tyrosine kinase receptor with extensive homology to the Epidermal Growth Factor Receptor (EGFR) which is the prototypal member of this family of receptor tyrosine kinases. HER-2 gene amplification is found in 20-30% of breast cancers. Various methods such as immunohistochemistry, southern and slot blotting, enzyme immunoassays and fluorescence in situ hybridization have all been employed to evaluate HER-2 gene and protein abnormalities. Of these immunohistochemistry is the most frequently employed but there are valid indications for the other avaliable methods. However, it is prudent that whichever methods employed are standardized, especially those that possess may have a degree of subjectivity in their assesment.