Renewed interest in N₂-fixation in cereals, grasses and sugar cane has occurred with the discovery of many new diazotrophic bacteria. After the introduction of N-free semisolid media, 15 years ago, for the isolation of root associated diazotrophic bacteria, a large number of more or less well defined new species have been described and characterized. Among then the more recent ones are three new species of Azospirillum: A. amazonense, A. halopraeferans and A. irakense which have been isolated from cereal and grass roots and some other plants. The remarkable adaptation of A. halopraeferans and also of the common Azospirillum species to saline soils and high temperatures has been demonstrated. A new genus, Herbaspirillum seropedicae, with characteristics very similar to azospirilla, has been found, on and within roots of maize, rice, sorghum and wheat in Brazil. Recently this bacteria was also isolated from sugar cane leaves and stems and a group of misclassified sugar cane pathogens named Pseudomonas rubrisubalbicans were found to fix N₂ and to be genetically very close to Herbaspirillum. Most recently a diazotrophic acetic acid bacterium was isolated from stems and roots of sugar cane and identified as a new species of Acetobacter, A. diazotrophicus. This N₂ fixing bacterium was also isolated from roots, tubers and stems of sweet potato but not from soil or other plants. These and the two aforementioned diazotrophs isolated from sugar cane seem to have endophytic habitats.