In this study samples were collected from the major soybean production areas of Adana and Içel province. The Rhizobium population of soils were determined in the greenhouse experiments. Enumeration of rhizobia populations using Most Probable Number Technique indicated a range of 0 to 3.1 x104 viable rhizobia/g soil for Bradyrhizobium japonicum. We compared the symbiotic effectiveness of native populations with one Ievel of N. Both higly and Iow effective isolates were found. The capability of two Bradyrhizobium japonicum strains to fix atmosferic nitrogen and the competition with indigenous population and among each other in forming nodules were studied. According to the results of the study USDA-11 0 was found the most effective strain.