Investigations were carried out onVigna unguiculataL. Walp. to estimate the distribution and utilization of15N in different organs after stem injection during vegetative, flowering and pod filling stage. During flowering effects of water deficit were also examined. In well watered plants, within 4 days after injection, 65% of15N accumulated in leaves. This was drastically reduced to 42% by water deficit.15N accumulation in stems increased under water deficit. The translocation of15N from the stem base to roots were not altered by water deficit. During pod filling 62% of recovered15N in the plants had accumulated in seeds, 24% in leaves and 11% in stems within 4 days, whereas the uptake of nitrogen in pod walls and roots remained low (2%). These results demonstrate that the method of injecting very small quantities (1 mg/plant) of15N into the stem base allows an exact and detailed quantitative assessment of N translocation/distribution with regard to different organs, different growth stages and different treatments.