We have formed planar tunnel junctions between Pb films and YBa2Cu3O7- single crystals with different surface oxygen stoichiometries. Oxygen losses have been induced by heating the crystals at 400°C in vacuum for different times. Low-leakage tunnel junctions have also been obtained in the case of the most degraded samples. As the oxygen deficiency increases, the Y-Ba-Cu-O gaplike structure gradually broadens and shifts towards higher energies. For thermally untreated samples, tunneling spectroscopy gives information on the local Tc.