Strains of Xanthomonas campestris pv. malvacearum races 2, 7,10, and 18 were mutated with the transposon TN903. The plasmid pRK2013 that contains TN903, wide host range transfer functions, and narrow host range replication functions was conjugated into the pv. malvacearum strains. TN903 confers resistance to kanamycin; consequently, transfer and incorporation of the transposon was accomplished by selection on media containing kanainycin. Since the plasmid does not replicate in Xanthomonas, kanamycin resistant strains were presumed to have TN903 integrated in to pv. malvacearum genomic DNA. Fluorophenylalanine resistant strains of pv. malvacearum were isolated that received TN903 at a higher frequency than the wild-type strains. Purine, tryptophan, isoleucine, ar thiamine, and thiamine auxotrophs were isolated.