Abstract: Since their original isolation from rice paddies near Hanoi, the set of microbial strains comprising the biofertilizer BioGro have been subjected to extensive and intensive experimentation in both laboratory and the field. Based on a hypothesis that such strains inoculated onto rice and other plants could significantly reduce the need for chemical fertilizers, this has been successfully tested using numerous procedures, documented in a series of peer-reviewed papers. The BioGro strains have been examined by a range of molecular and biochemical techniques, also providing means of quality control of inoculants. A positive response by rice plants to BioGro strains has been confirmed by proteomics. More than 20 randomized block design field experiments conducted in Vietnam or Australia have confirmed their effectiveness under a range of field conditions, reviewed here. Interactions with different rice cultivars have also been examined. While the response to inoculation is complex, the hypothesis of increased nutrient efficiency has been amply confirmed as consistent with observations. Finally, an extensive participatory research project over 3 years in the Mekong Delta showed reductions in fertilizer needs as high as 52 % as rice farmers learned to apply the technology. This result shows the importance of such adaptive practices for successful application of this biofertilizer technology in field condition.