Fly ash and its different combinations with soil (w/w) were tested to explore its possible use as a potential carrier for diazotrophs and phosphobacteria. Azotobacter chroococcum, Azospirillum brasilense and Bacillus circulans showed their maximum viability in fly ash alone whereas Pseudomonas striata proliferated most in soil:fly ash (1:1) combination. (C) 2004 Elsevier Ltd. All rights reserved.