Efficient use of nitrogen (N) by plants and particularly crops, is of global importance. In agriculture, high crop yields and protein content depend upon extensive N-inputs, however fertilizer N is costly to the farmer, and overuse can be damaging to the environment. A critical component of optimised usage is efficient capture by crop root systems. This chapter focusses on principal mechanisms of uptake and factors influencing efficiency. Genetic variation in root architecture and in an array of transporters known to be involved in nitrogen capture is detailed. The impacts of abiotic stress factors such as soil structure are described. Finally prospects and opportunities for crop improvement are discussed.