Nineteen Rhizobium isolates were screened for effectiveness in nitrogen fixation with groundnut cv. Virginia Florigiant. Strains exhibited wide variation in effectiveness. Five strains were marked with either streptomycin or kanamycin and used as inoculants in field studies. Assessment of strain competitive ability was complicated by isolation of kanamycin-resistant strains from uninoculated plots. Inoculation appeared to increase groundnut yields.