The photodoping kinetics of silver into glassy As–S films, induced by pulsed excitation, has been studied. The electrical resistance of the metallic silver layer changes instantaneously after excitation with a time constant of about 50μs, which is nearly the same as the response time of photoconduction in the silver-doped sample. These observations suggest that the silver movement in the photodoping process is triggered by the silver penetration into the photodoped region, which is caused by an increase in the conductivity in the doped region.