The desulfurization kinetics of Nocardia globerula R-9 was investigated initially in a model system consisting of dibenzothiophene (DBT) dissolved in dodecane. The ability to desulfurize straight-run diesel oil by resting cells of this strain was also evaluated. The course of desulfurization of DBT in dodecane could be represented by the Michaelis-Menten equation. The desulfurization of DBT and 4,6-dimethyl dibenzothiophene (4,6-DMDBT) in a mixture of the two proceeded simultaneously without preference for either of them. The sulfur content of the straight-run diesel oil could be reduced from 1807 to 741 mg dm(-3) by treatment with resting cells of this strain, at a mean rate of 5.1 mmol sulfur kg(-1) h(-1). This showed that Nocardia globerula R-9 could be a potential bacterium for reducing the sulfur content of petroleum products. (C) 2003 Society of Chemical Industry.