[en] Nitrogen (N) use efficiency (NUE) of fertilizer N can be accurately estimated by tracing the fate of soil applied labelled fertilizer, but the quantity of N remobilization from non-kernel components into kernels in maize (Zea mays L.) plants is difficult to determine. A field experiment involving stem infusion with labelled 15N solution was conducted at Ottawa, Ontario (45 degrees 22'N, 75 degrees 43'W) for two years to determine whether stem infused 15N could be used to quantify N remobilization and the contribution of remobilized N to the grain. A current stay-green commercial hybrid was grown at three fertilizer N rates and infused with 30 mL 15N solution [35.7 mmol N as 15NH(4)15NO(3) at 99.2 15N% atom enrichment (a.e.)] into the internode below the primary cob at anthesis. The control plants were infused with distilled water. Sampling occurred at 3 d, 2 wk and 5 wk after anthesis and at physiological maturity