Objective: Overexpression of the ERG protein is highly prevalent in prostate cancer (PCa) and most commonly results from gene fusions involving the ERG gene. Recently, an N-terminal epitope targeted mouse and a Cterminal epitope targeted rabbit monoclonal anti-ERG antibody have been introduced for the detection of the ERG protein. Here, we are the first to compare the mouse ERG-MAb to the rabbit ERG-MAb for their concordance on the same PCa cohort. Furthermore, we assessed if the ERG protein expression is conserved in lymph node and distant metastases. Method: We evaluated tissue microarrays of 278 specimens containing 265 localized PCa, 29 lymph node, 30 distant metastases, and 13 normal prostatic tissues. We correlated the ERG protein expression with the ERG rearrangement status using an ERG break-apart fluorescence in-situ hybridization (FISH) assay and IHC of both ERG antibodies. Results: ERG protein expression and ERG rearrangement status were highly concordant regardless of whether the mouse or rabbit ERG-MAb was used (97.8 % versus 98.6 %, respectively). Conclusion: This is the first study to comprehensively compare the two ERG-MAbs. By demonstrating a broad applicability of IHC to study ERG protein expression using either antibody, this study adds an important step towards a facilitated routine clinical application.