Total electrical conductivity and thermoelectric power measurements of polycrystalline Y2Ti2O7 were made at 1373, 1273, 1173 and 1073 K under the oxygen partial pressure, p(o2), between 10(-23) and 1.0 atm using Ar+O-2, H-2+H2O, H-2+CO2, and CO+CO2 gas mixtures. The partial conductivity of electrons was predominant at low p(o2) region, being proportional to p(o2)(-1/4), and a small contribution of the partial conductivity of holes was observed at high p(o2) region. The partial conductivity of oxide ions without p(o2) dependency was predominant in high, p(o2) region. The partial thermoelectric powers of electrons, holes and oxide ions were evaluated from the total thermoelectric power measurements using the transference number of carriers estimated from the conductivity data, and the electrical transport properties of electrons and holes, i.e. the apparent band gap and mobility of electrons and holes were discussed.