Recent work has indicated that residual contamination on III‐V substrates has an adverse effect on epilayer nucleation. This letter presents preliminary results of measurements of contamination levels on methanol‐bromine polished ion‐cleaned (100) InP substrates using low [primary ion dose (<5×1012ions mm−2) secondary ion mass] spectrometry (SIMS). Even after ion etching ≃0.48 &mgr; from the surface residual contamination levels in the 100‐ppm range persist, the largest being oxygen. Micrographs of the ion‐cleaned surface showed precipitation of In at the surface which was caused by differential sputtering effects.