Amorphous Ge-As-X (X = S or Se) films have been evaporated on Si substrates. The mechanical stress created in the system of film and substrate has been studied by Newton rings method. The mechanical stress in fresh films is compressive and slightly depends on the film composition. After bandgap illumination and/or annealing, a stress transition effect is observed due to the irreversible photo-and thermo-structural changes occurring in the film. The Ge-As-S amorphous films are more sensitive to photo-and thermo-induced changes than the Ge-As-Se films and the stress is smaller in the latter. The explanation of the obtained results is based on the changes in the short-and medium-range order in the amorphous film structure.