Chlorine is one of the most used species to produce n-type ZnSe epilayers. In this paper, we present Secondary Ion Mass Spectrometry (SIMS) profiles of a series of Cl -doped ZnSe samples, which were grown by Molecular Beam Epitaxy (MBE) technique on GaAs substrates. These profiles have been used to examine the limitation of SIMS analysis of narrow Cl -delta layers. In order to convert SIMS raw data to quantified data, the depth profile from a Cl -implanted standard sample has been used to estimate the "useful ion yield" of chlorine and thus the instrumental sensitivity for chlorine in a ZnSe matrix. The "useful ion yield" and detection limit of chlorine in the ZnSe host matrix were calculated to be 4.7 × 10-7 and 5 × 1017 atoms/cm3, respectively.