Objectives: To compare the INFORM HER2 bright-field dual in situ hybridization (DISH) DNA probe cocktail assay with the PathVysion fluorescence in situ hybridization (FISH) assay on 103 invasive breast carcinomas with a 2+ score on immunohistochemistry (IHC). Methods: The cases were categorized as positive, equivocal, or negative for HER2 gene amplification using the 2007 American Society of Clinical Oncology/College of American Pathologists (ASCO/CAP) HER2:CEP17 ratio criteria and also based on mean HER2 gene copies/cell. The third criterion used a HER2:CEP17 ratio of 2 to categorize cases as positive or negative. Results: The agreement between FISH and DISH was 85% using the 2007 ASCO/CAP ratio criterion, 79% using the mean HER2 gene copies/cell criterion, and 92% using the 2.0 cutoff HER2:CEP17 ratio criterion. In addition, 20 known IHC 3+ breast carcinomas analyzed by DISH showed clusters of the HER2 gene consistent with unequivocal amplification. Conclusions: Despite some technical and interpretational issues associated with DISH, it compares favorably with FISH in this group of challenging breast cancer cases.