Abstract: Synthetic Ag-doped PbS samples were Ar ion beam milled and examined by HRTEM. The silver was found to aggregate in inclusions which have no crystallographic relationship to the PbS host, rather than forming crystallographic defects. The Ag2S inclusions are 500 Å in diameter or larger. The limit of Ag substitution into PbS in solid solution in the absence of Bi or Sb is less than 0.1 mol %. The ion beam milling process introduced a large number of small dislocations in both Ag-doped and pure PbS specimens. These dislocations are thought to be formed through coalescences of point defects.