252 bacteria strains were isolated from different internal tissues of cotton cultivars collected from Xinjiang regions. These strains were preliminarily classified as Bacillus sp., Xanthomonas sp., Pseudomonas sp., Erwinia sp., and Curtobacterium sp. Among these five genera,Bacillus sp. was the most prevalent endophytic bacterium in cotton. Results indicated that population densities of endophytic bacteria ranged from 1.0×10 to 1.4×10~8 cfu/g fresh weight although it might vary depending on cultivar...