Biological nitrogen fixation is largely dependant on soil conditions. Lack of water causes increased salt concentration and elevated osmotic pressure in the soil, which negatively affect the symbiotic relationship between plant and bacteria, and nitrogen fixation itself. In this master thesis, fifteen indigenous strains Bradyrhizobium japonicum isolated from five different regions of the Republic of Croatia were subjected to in vitro investigations in drought conditions and with increased concentrations of NaCl. Identification of strains was carried out with ERIC-PCR method in order to determine genetic variability of indigenous bacteria. Conditions of in vitro water deficiency were determined with polyethilene glycol (PEG) 6000. At 15 % of PEG 6000 indigenous strain isolated from east Slavonia region, B. japonicum IS1 is tolerant to the lack of water. Least resistant strain is B. japonicum ZS4, isolated from west Slavonia. At the concentraction of 30 % PEG 6000, indigenous strain from eastern Slavonia, B. japonicum IS2, is distincively resistant to osmotic pressure and least tolerant is strain B. japonicum IS4, from eastern Slavonia. In all tested strains, good growth is observed at the concentration of 1 % NaCl. Moderate growth is noticed in the indigenous strain from Koprivnica region and in the referent strain B. japonicum 344, whilst two strain from western Slavonia are intolerant at 2 % NaCl. Two indigenous strains of Baranja region, one from Istria, three from eastern Slavonia and one from Koprivnica region are resistant on the salinity of 3 % NaCl. Indigenous strans from Baranja region, Istria and two from eastern Slavonia are very tolerant on the high concentration of 4 % NaCl. According to results from ERIC-PCR method genetic similarity is not conditioned with location of the isolation. All strains are divided into two main groups with low relative similarity. The greatest genetic similarity were observed with strains that were isolated from Baranja region, easter Slavonia, Koprivnica and western Slavonia.