Thermoelectric power and electrical conductivity of SrCe0.95Y0.05O3-delta have been determined in a range of atmospheres and temperatures. The thermoelectric power is negative in reducing and positive in oxidizing atmospheres. The data indicate a transition at about 800-1000 degrees C at oxygen partial pressure approximate to 10(-5) atm between regimes with different type of main charge carrier. Low oxygen partial pressure data do not indicate any conductivity contribution from n-type electronic carriers. The water vapour partial pressure dependence is found to be in accordance with theory and shows that these experiments can be used to detect proton conductivity.