The isotopic comparative method (ICM) has been used to measure the concentrations and relative ion yields of Si+, Ge+ (Si-, Ge-) in SiGe alloys ranging almost from pure silicon to pure germanium by secondary-ion mass spectrometry under Ar+ bombardment at 8 keV, ~39° incidence, (17 keV, ~25°). This method requires only two specific ICM reference samples to be fabricated. The negative-secondary-ion yields YR−(Si) and YR−(Ge) are found to be nearly constant over the entire range of SiGe alloy. The measurement conditions are free of matrix effects, thereby allowing accurate and easy quantification of SiGe alloys. In contrast, the positive-secondary-ion yield YR+ (Si) decreases strongly over the full range of SiGe alloy, whereas YR+(Ge) varies only slightly for cGe < 25 at.%. Copyright © 2012 John Wiley & Sons, Ltd.