Oestrogen influences both oxytocin mRNA and peptide immunoreactivity in the preoptic area and the rat oxytocin gene contains functional oestrogen response elements. However, using combinations of immunocytochemistry and in situ hybridization for oxytocin and oestrogen receptor, we found that preoptic oxytocin neurones do not possess oestrogen receptors. This finding implies oestrogen actions on oxytocin synthesis in preoptic neurones are unlikely to be mediated directly.