Breast cancer represents the most common type of cancer in women worldwide and the fourth leading cause of cancer deaths in Australia. Management of breast cancer relies largely on hormone-receptor biomarkers, but the heterogeneity of the disease impedes prognosis and treatment. In recent years, the involvement of the oxytocin receptor, well known for mediating milk ejection from the mammary glands, in breast cancer has become apparent. The oxytocin receptor is expressed in breast cancer cell lines and mice xenografts, and some studies observed that oxytocin has a modulatory effect on tumour growth. In cells and tissues, the detection of oxytocin receptor by immunohistochemistry is currently hindered by the lack of receptor subtype-specific antibodies and requires additional methods such as RT-PCR to confirm their presence at a membrane/protein level. Selective oxytocin analogues have been developed and can be functionalised with fluorophores for imaging or radioisotopes for targeted treatment. In this project, we are developing novel and advanced tracers that can target and visualise breast tumours expressing the oxytocin receptor. These probes will provide the necessary tools to selectively study oxytocin receptor in vitro and in vivo and determine its potential as a drug target in breast cancer.