Introduction: HER2 protein over-expression or gene amplification is detected in approximately 20% breast tumours, is associated with an aggressive phenotype and is predictive of response to trastuzumab therapy. The use of chromogenic in situ hybridisation (CISH) for evaluating HER2 status routinely is recognised in much of Europe but has yet to achieve widespread acceptance in the UK. Methods: CISH analysis for HER2 status was performed on 161 breast cancer cases. Results were compared to immunohistochemistry (IHC) and dual colour fluorescent in situ hybridisation (FISH) data. Results: There was 100% concordance between CISH and FISH but only 93.8% concordance between CISH and IHC. Performing CISH 'in-house' was found to cost approximately 50% less than the FISH / IHC protocol at the reference laboratory. Conclusion: It is concluded that CISH is as accurate as FISH for diagnostic purposes and is more cost-effective than the IHC / FISH regimen currently favoured in the UK.