The Ag diffusion in the superconducting oxide ceramic Bi1.6Pb0.4Sr2Ba2Cu3Ox has been studied over the temperature range 350-800 degrees C using the technique of successive removal of thin layers and measurement of the sample resistivity. The temperature dependence of the Ag diffusion coefficient is given by the relation D = 5.2 x 10(-3) exp(-0.70/kT). The observed fast Ag diffusion is assigned to impurity migration through the defects of ceramic samples (the surface of pores, grain boundaries etc.). The current-voltage characteristics of Ag-Bi(Pb)-Sr-Ca-Cu-O-Ag structures at room temperature became markedly degraded. It is discussed in relation to the redistribution of Ag via diffusion (with D approximate to 10(-12) cm(2) s(-1)) from the metallic layer into the superconductor.