Since 1988 the CIRAD-Forêt Agroforestry Program has carried out several fines of research on the utilization of Calliandra calothyrsus in agroforestry systems in Reunion Island, Burundi, and New Caledonia. In order to optimize the yield of C. calothyrsus hedges, we have investigated the rhizobium requirement of C. calothyrsus for forming nodules and fixing N2. This species is found to be specific for both nodulation and effectiveness. We have observed significant differences within our collection of Rhizobium strains established from C. calothyrsus nodules collected in Reunion Island, Kenya, New Caledonia, and Singapore. When seedlings of C. calothyrsus were inoculated with these Rhizobium strains, it was possible after three months in the greenhouse to identify strains that significantly improved the growth and shoot N content of C. calothyrsus in comparison with uninoculated plants and plants inoculated with strains from the NifTAL collection. The next step in our study is to verify the symbiotic behavior of laboratory-selected Rhizobium strains in field conditions in New Caledonia and determine how inoculation with them affects the yield and forage quality of C. calothyrsus.