Parathyroid hormone related protein (PTHrP) is a novel calcium regulating hormone that may have a significant role in the pathophysiology of breast cancer. We have previously demonstrated a relationship between immunohistochemically detectable PTHrP in primary breast tumours and the subsequent development of bone metastases and hypercalcaemia. The aim of this study was to compare the PTHrP status in the primary tumours from three groups of patients with widely varying prognosis.(1) The favourable outcome group; all patients had a favourable prognosis and minimum 3 years disease free follow up (n= 30).(2) The unfavourable outcome group; all patients presented with localized breast cancer but developed distant disease within 3 years (n= 26).(3) The unfavourable presentation group; all had distant disease at first presentation (n= 26). No differences in PTHrP status of the primary tumour amongst the three patient groups were found (66%, 65% and 61% positive respectively). The development of bone with liver metastases and hypercalcaemia was associated with increased positive PTHrP status of the primary tumor.