A method for determination of As, Cr, P, Pb, Si, and V in ethanol fuel by inductively coupled plasma tandem mass spectrometry (ICP-MS/MS) is described. Samples were simply diluted in 1% (v/v) HNO3, and a matrix-matching strategy was used for calibration. The analytical performance of ICP-MS/MS operated in both single quadrupole and tandem mass spectrometry (MS/MS) mode with and without introducing oxygen into the octopole reaction system (ORS3) was evaluated. Addition and recovery experiments in ethanol fuel samples for determination of As, Cr, P, Pb, Si, and V were carried out to investigate the accuracy of the method, and recoveries ranged from 84 to 109% for all analytes by mass shift mode. Accuracy for Cr, P, and Si determinations was only achieved by monitoring their oxide ions by MS/MS mode, and in the case of Si determination, its dioxide ion ((SiO2+)-Si-28-O-16) was monitored with the ORS3 pressurized with 0.3 mL min(-1) oxygen gas. The combination of MS/MS and mass shift modes allowed for the successful determination of all target analytes.