Since its rediscovery in the 1970s, Azospirillum has created countless expectations. At the beginning, it was thought that an Azospirillum inoculation at sowing was the definitive solution to provide nitrogen to grasses, avoiding the use of nitrogen fertilizers. However, the results were not always visible. It was still unclear why about half of the field trials, unlike the experiments conducted in vitro under controlled conditions, did not produce positive effects. The first experiments conducted in vitro on Azospirillum and Arthrobacter co-cultures showed how Azospirillum was stimulated in some of its interactive functions with the plant by other bacteria. Subsequent field experiments conducted on various plants inoculated with Azospirillum in consortiums with different selected bacteria have instead shown consistently positive results. Azospirillum, being the most intensively studied plant growth-promoting rhizobacteria (PGPR), remains one of the best and most reliable PGP bacteria, and it is the best documented case of a plant-hormone producer. It associates with many cropCrops plants, works very well in consortium with other bacteria, and penetrates inside the host plant, where it can interact very closely with the host. In conclusion, especially in consortiums with other selected bacteria, Azospirillum remains one of the most interesting plant probioticProbiotic to be used in field inoculations.