Air‐ and vacuum‐cleaved rocksalt crystals have been treated with H2O vapor and with a mixture of H2O vapor and CO2gas in order to study the influence of such contaminations on the epitaxial growth of gold films on NaCl crystals. Hydroxide surfaces resulting from the treatment with pure H2O vapor yielded epitaxial gold films on both vacuum‐ and air‐cleaved specimens and these were very similar in nature to those epitaxial films normally grown on air‐contaminated NaCl substrates. Bicarbonate surfaces resulting from the further treatment with a mixture of H2O vapor and CO2gas yielded polycrystalline gold films on both the air‐ and vacuum‐cleaved specimens.