Recalcitrant organosulfur compounds such as Dibenzothiophene (DBT) and its derivatives in real petroleum fractions such as diesel cannot be removed by convectional hydrodesulfurization (HDS) treatment using metallic catalysts as well as extremes of conditions of high pressure and temperature. Biodesulfurization was identified as one of the possible routes for the removal of sulfur from middle distillate fractions of petroleum. The desulfurizing bacterium Desulfobacterium indolicum was isolated and subsequently identified by the Department of Botany and Microbiology, University of Lagos, Nigeria. The bacterium exhibited very high desulfurizing ability towards diesel at 30 degrees C and normal atmospheric pressure. The biodesulfurization of diesel by Desulfobacterium indolicum resulted in reduction of sulfur from 166.037 ppm to 33.412 ppm over a period of 72 hours. Gas chromatography analysis with a pulsed flame photometric detector revealed that the peaks of benzothiophene and dibenzothiophene significantly decreased after biodesulfurization. Thus, Desulfobacterium indolicum could effectively desulfurize diesel and therefore, may be a promising biocatalyst for practical biodesulfurization of diesel.