We have shown that small concentrations of metal atoms on UV/ozonized GaAs wafer surfaces can be quantitatively determined by time-of-flight secondary ion mass spectrometry (TOF-SIMS). As standard reference materials, we produced defined submonolayer concentrations of Ca, Mg, Al, Cu, Zn, Si, Ni, Cr, Co, and Fe on the wafer surface by sputter deposition from different single- and multielement targets. The concentrations of the elements withm>27u involved in these calculations were verified independently by total reflection x-ray fluorescence spectroscopy. For all ten metals, a linear relation exists between the relative metal signalMe+/71Ga+and the surface concentration of the metal. By this relation we established TOF-SIMS sensitivity factors for these metals on UV/ozonized GaAs. The detection limits for almost all elements are in the order of109atoms/cm2.