In calcareous soils the yield of grain legumes is often limited by the lower availability of iron (Fe), especially when they depend upon symbiosis with root nodule bacteria for their N nutrition. In order to explore the variability of responses of N-2-fixing common bean to Fe deficiency the common bean white-seeded lines Striker and Coco blanc, and coloured-seeded tines SVM-29-21 and ARA14 were inoculated with Rhizobium tropici (CIAT 899) and cultivated hydroaeroponically with a N-free nutrient solution supplied or not with 45 mu M Fe. Differences among lines were observed: Fe-deficiency-induced-chlorosis on young leaves was earlier and more severe in some lines than others. Nodule development and N-2-fixing capacity was less affected in tine ARA14 which preferentially allocated Fe towards nodules. Results suggest that Fe use efficiency for symbiotic nitrogen fixation (FeUE SNF) could be used to screen tolerant bean tines to Fe deficiency in condition of symbiotic nitrogen fixation