Nitrogen use efficiency (NUE) from soil to plant is an important trait to consider with respect to grassland improvement since it impacts on fertiliser use and nitrogen pollution of waterways. Perennial ryegrass (Lolium perenne L) is the most important grass species of temperate grasslands and QTL for NUE, both uptake and utilisation of N, have been characterised in a series of experiments conducted in flowing solution culture providing precise control of N form and concentration. Acquisition and utilisation efficiencies of N were characterised under growth-limiting and non-limiting concentrations of nitrate or ammonium. Significant QTL for uptake and utilisation efficiencies, and for their component traits, were observed in all cases. The presentation will examine the QTLs detected and how they were affected by the source and the concentration of nitrogen supplied. The presentation will also include the ways identified QTLs are bred into elite ryegrass genotypes using conventional and marker assisted breeding approaches.