With the isotopic comparative method (ICM), we determined the ion yields of B+, O+, Si+, B−, O−, and Si− versus oxygen concentration in silicon under Ar+ bombardment. By multi-energy implantation, we obtained samples containing a near-uniform low concentration of 18O, which we then implanted with a high dose of 16O. The ICM allows us to determine the oxygen concentration profile as a function of substrate depth during analysis by secondary-ion mass spectrometry, following which the ion yield is measured as a function of oxygen concentration from 0 to 33 at.%. The results show that, whatever the charge of secondary ions, all relative ion yields are enhanced with increasing of oxygen concentration. Very strong matrix effects due to oxygen are found for B+ (>100), whereas moderate or slight matrix effects are found for Si+ and O− (>10) and for Si−, B−, and O+ (<4). Whereas the relative ion yields of B+ and Si+ differ (as a function of oxygen concentration), the relative ion yields of B− and Si− are identical. The relative ionization probability versus oxygen concentration for Si+ agrees very well with the results of William's group. Copyright © 2012 John Wiley & Sons, Ltd.