A high energy ion which is directed near close-packed rows or planes of atoms in a single crystal is steered (channeled) into the spaces between these rows or planes.1–3A channeled ion is deflected out of the channel (is dechanneled) when its transverse energyE⊥exceeds a critical valueEc⊥. The ion then becomes part of the random beam, if rechanneling is neglected. An ion can be dechanneled by electronic collisions or by nuclear collisions with displaced atoms. Displacements in the form of thermal vibrations4–6or radiation damage7, 8can cause large increases in dechanneling. We have investigated whether the dechanneling caused by thermal vibrations and that caused by permanent displacements (in the form of radiation-induced point defects) are additive for an Al-0.08% Ag alloy.