The volume change due to substitutional and interstitial helium atoms : n V, Fe, Mo, Ta, and W has been determined using the displacement fields from previously reported model calculations. Interstitial He produces a lattice expansion of less than one atomic volume in all metals studied, ranging from 0.4 to 0.9 Ω. The volume change for substitutional He in a given metal is 0.6 ± 0.1 Ω less than that for interstitial He in that same metal.