COX2 and HER2 expression are associated with a poor prognosis in prostate cancer and HER2 has been linked to COX2 expression in colorectal cancer. The association between COX2 and HER2 expression was investigated in 117 patients with prostate cancer (89) or Benign prostatic hyperplasia (BPH) (28). Tissue was analysed for HER2 amplification by fluorescent in situ hybridisation, and HER2 and COX2 protein expression by immunohistochemistry (IHC). All tumours analysed expressed COX2 at a significantly higher level than BPH tissue (P=0.041). Only low levels of HER2 gene amplification (8%, 7/89) and HER2 protein expression (12%, 11/89) were observed. HER2 protein expression was rarely observed and did not correlate with HER2 amplification or COX2 expression. Although HER2 does not drive COX2 expression in prostate cancer, this study identified high levels of COX2 expressed in locally advanced prostate cancer, suggesting COX2 could be a potential therapeutic target. COX2 inhibitors are currently being used in clinical trials for the treatment of other tumour types.