A biotechnological method for fuel desulfurization is described. The method includes the steps of biocatalytic oxidation of organosulfides and thiophenes, contained in the fuel, with hemoproteins to form sulfoxides and sulfones, followed by a distillation step in which these oxidized compounds are removed from the fuel. Straight-run diesel fuel containing 1.6% sulfur was biocatalytically oxidized with chloroperoxidase from Caldariomyces fumago in the presence of 0.25 mM hydrogen peroxide, The reaction was carried out at room temperature and the organosulfur compounds were effectively transformed to their respective sulfoxides and sulfones which were then removed by distillation, The resulting fraction after distillation contained only 0.27% sulfur. Biocatalytic oxidation of fuels appears as an interesting alternative to biodesulfurization.