Abstract: Occurrence and distribution of heterotrophic soil bacteria and an important associative microaerophilic nitrogen fixing Azospirillum from the rhizosphere of Taro (Colocasia esculenta L. Schott.) was studied. Samples of Taro root and rhizosphere soil were collected from ten different sites of Jahangirnagar University campus. Organisms were found to occur in root and rhizosphere soil of Taro. The quantity of both total heterotrophic bacteria and Azospirillum spp. in two different samples varied significantly with the range of 7.55x106 to 97.66x107 and 0.1x106 to 11x106 MPN g-1 dry wt., respectively. Rhizosphere soil was found to harbor the highest population of both types of organisms. The nitrogen fixing potential of ten isolates of Azospirillum spp. was also determined in an enrich medium. As per the efficiency of nitrogen fixation (2 to 6.16 mg N g-1 substrate) the isolated Azospirillum strains could be arranged as J-4>J-6>J-3>J-9>J-5>J-7>J-2>J-10>J-8>J-1.