The effective chemical diffusivities in the proton conductors SrCe0.95Yb0.05O3-alpha and SrZr0.95Yb0.05O3 were determined electrochemically. After setting up a proton concentration gradient using the Hebb-Wagner technique, the temporal evolution of the voltage across the electrolyte was measured which permitted the extraction of the proton diffusivities. Using the usual representation D=D(0)exp(-Delta H/kT) we obtained for the cerate in the temperature range 300-600 degrees C:D-0=0.002185 cm(2)/s and Delta H=0.46 eV; and for the zirconate in the same temperature range : D-0=0.0137 cm(2)/s and Delta H=0.58 eV.