aA series of experiments was planned for practical application of rhizobia in grass lands in Korea. This is the report for the studies mainly on the isolation and characterization of alfalfa nodule bacteria, and on the assessment of their nodulation abilities and nitrogen fixation capacities. 1. Total number of 47 strains was isolated from nodules which were taken from alfalfa grown in Daekwanyong, Cheju and other places. 2. Morphological and cultural characteristics cf the strains were studied, and attempts. were also made to investigate their antigenic properties and to demonstrate lysogenic strains. The results were: ⅰ) the isolates varied in their cultural characteristics on yeast mannitol broth and agar, and in degree of Congo red absorption: ⅱ) similarities in their antigenic properties were found between the strains: SU 47/M-11, M-13/M-15, and M-3/ M-5; ⅲ) no lysogeny was found in the strains. 3. Plant infection test by test tube method in light room were carried out to elucidate the ability of the strains to nodulate Luna alfalfa and of the capacity of such nodules to fix atmospheric nitrogen. The isolates were grouped into non-invasive, ineffective, or effective to the legumes. Those strains which produced effective nodules, supporting similar/higher level of growth as nitrate control were: M-8, 9, 14, 20, 21, 25 and 34.