The influence of In and Ag atoms on the dc electrical conductivity and optical properties in the short wavelength edge region in Ge20Sb10S70 and Ge30Sb10S60 glasses has been examined. Contrary to the effect of In atoms, the Ag atoms at concentration levels below 4 at. % of Ag significantly influence the dc conductivity. Changes of the optical properties are less significant, and they are affected in a similar way by incorporation of In and Ag atoms into a glassy matrix. It is supposed that some of the Ag atoms are positively ionized to an Ag+ species that remains in the network. The 5s1 electron of Ag interacts with D+ states making, in the final state, an increase of D− defect states. Thus the Fermi level is shifted to the valence band and the dc conductivity increases.