"Biotechnology of Biofertilizers" covers the basic issues in biological nitrogen fixation like physiology, biochemistry and molecular genetics of nitrogen fixation, role of signal molecules and host gene expression in nodulation and nitrogen fixation for a thorough understanding of these processes in symbiotic nitrogen fixing system and the possibilities of extending these agronomically potential and significant processes to non-legumes. The potential benefits from the N2 fixing symbiotic system such as Sesbania rostrata, Azola, and free-living cyanobacteria to rice crop and associative symbiotic N2 fixer Azospirillum rain fed crops have been discussed in detail along with recent developments in biofertilizer technology such as immobilization of cyanobacteria for maximizing ammonia production in rice soil ecosystem and endophytic nitrogen fixation in wheat. The solubilization and mobilization of nutrients by phosphobacteria and VA mucorrhiza and their role as bioinoculants, Acetobacter diazotrophicus as a novel biofertilizer for sugarcane and the cycad - cyanobacterial symbiosis have been clearly elucidated.