An extensive search for active (acetylene reducing) nitrogen-fixing root nodules was made amongst Brazilian forest legumes. Seven new nodulated species, including two new nodulating genera, were found in the Caesalpinioideae, 18 new species in the Mimosoideae and 30 new-species, including four new genera, in the Papilionoideae. All have potential importance in reafforestation. Fifty-eight new records of non-nodulating species are included. The morphology of all nodules was studied and is discussed in relation to taxonomic position. Preliminary data on nodule structure are given.