An oxidative-desulfurization (ODS) process was used, instead of the conventional hydrodesulfurization (HDS) process, to remove sulfur from diesel fuel. This ODS process comprises two stages: oxidation using H2O2 and acetic acid, followed by solvent extraction with dimethylsulfoxid (DMSO) which having the capability to dissolve sulfur and aromatic compounds. The extraction efficiency for diesel fuel was improved by preceding the extraction with oxidation. The phase equilibrium data and the ternary miscibility diagram of the system oxidized diesel fuel-DMSO have been investigated and determined. Countercurrent multiple contact extraction results for the previous system were derived from the phase equilibrium data both by construction and calculation methods. The minimum and maximum amounts of the solvents (S-min and S-max) that may be used, which define the final extract and raffinate phases (E-m and R-m) were estimated from the ternary equilibrium diagram. Also the number of theoretical stages needed for the production of the desired product (R-m), yield, aromatic and sulfur contents of the raffinate and extract products using the studied solvent at various solvent/feed ratios (S/F) were determined. Thus this combination processes is capable of removing up to 98.6 wt.% of the sulfur compounds in diesel fuel at acceptable yield. (c) 2012 Elsevier B.V. All rights reserved.