Nitrogen (N) fertilisation is fundamental to achieving crop yields but the inefficient use of nitrogen fertiliser leads to major economic and environmental costs. Over the last twenty years there has been major public and private investment in improving the efficiency with which plants use nitrogen fertiliser, their nitrogen use efficiency (NUE), but with limited success. The reasons behind the inability to improve NUE are becoming clearer and technological advances pave the way for addressing these issues and making real progress. The major reason for the lack of progress in improving NUE is that, for a crop like wheat, what determines NUE differs greatly depending on environment and crop agronomy. Even within Australia, improving wheat NUE means very different things for winter rainfall crops in deep sandy soils of Western Australia compared with wheat crops on deep clays of Southern Queensland relying on stored summer rainfall. Global efforts, such as the Wheat Initiative, are cataloguing different wheat NUE scenarios to look for common targets, thus enabling better coordination of global activities. Despite the substantial transgenic based efforts to improve NUE, translation to improve field NUE has been disappointing. Transgenic approaches utilising better targeted promoters or gene editing have better chances of success than coarse constitutive promoter based efforts. They also allow long term projects such as nitrogen fixing cereals to be seriously attempted. The ability to more accurately phenotype nitrogen use efficiency is another key to making real advances in NUE. Advanced field based phenotyping platforms allowing detailed measurement of biomass and nitrogen status throughout the season can facilitate the unravelling of the genetic x environment x management interactions. Improved controlled environment phenotyping systems and non-destructive measurement of growth and tissue N offer the potential to further dissect the genetic basis of NUE.