Thin silver–gold single-crystal sandwich specimens consisting of a silver layer 700 ± 50 Å thick and a gold layer 850 ± 50 Å thick were bombarded along [001] at normal incidence to the silver layer with 40 keV gold ions at room temperature. A significant number of the gold ions became channeled along [001] and were able to reach the gold layer where they produced radiation damage in the form of "black-spot" defects visible by transmission electron microscopy. (The silver layer therefore acted as a filter which allowed only channeled gold ions to enter the gold layer.) A stereo analysis of black–white contrast from the defects in the gold layer revealed that they were all vacancy type. Further measurements and observations indicated that the vacancy defects were formed in situ at displacement cascades initiated by the dechanneling of the channeled gold ions at thermally displaced atoms. It is concluded that the stopping of channeled gold ions in gold at room temperature by dechanneling at thermally displaced atoms is a major stopping mechanism in the energy range where nuclear stopping becomes important.