We have examined the chemical stability of undoped and 5 weight percent Ag-doped YBa2Cu3O7-x thin films, both grown in situ by pulsed laser deposition technique. The studies indicate that Ag-doped films are more stable than undoped films. The improved chemical stability of Ag-doped films has been attributed to reduction in the effective area of intergranular regions and the presence of passivating silver clusters around grains. The study has also shown that coating the YBa2Cu3O7-x film surface with noble metals like Ag and Au results in passivation of YBa2Cu3O7-x films.