The significant and often unpredictable variations, or transient effects, observed in the secondary ion intensities of O+/- and Si+/- during the initial stages of depth profiling with Cs+ have been studied. These were found to be primarily due to two competing effects: (a) the steady accumulation of Cs in the substrate as a function of sputtering time and (b) the varying oxygen content from the native oxide as a function of depth. These effects prevail over depths approximated by similar to 2R(norm), where R-norm is the primary ion range normal to the surface. The Cs+ induced effects are consistent with a work function controlled resonance charge transfer process. A method for controlling these effects, namely the prior evaporation of Cs and use of an O-2 leak during analysis is described. Doped (As and Sb) and undoped Si wafers with similar to0.9 nm thick native oxides were analyzed using 0.75 and 1 keV Cs+ beams incident at 60 degrees. The more intense polyatomic AsSi- and SbSi- emissions did not exhibit these effects, although other relatively minor intensity fluctuations were still noted over the first similar to0.5 nm.