The electronic structure and diffusion paths of Ag ions in the rocksalt structured phase of AgI (rs-Agl) are studied based on the full-potential linear-muffin-tin-orbital (FP-LMTO) method. Ag ions in the rs-Ag1 start to migrate along the (I 11) direction due to the low energy barrier, as is well known in the cases of AgBr and AgCl. The high ionic conductivity in rs-Agl might be expected from the viewpoint of the empirical overlap parameters between Ag 4d electrons and halogen p electrons. (c) 2007 Elsevier B.V. All rights reserved.