The surface of YbBa2Cu3O7-δ single crystals was investigated using a scanning tunneling microscope at room temperature in air. Growth steps with step heights equal to the lattice parameter c as well as steps with step heights of multiples of 1.35 c were obtained. On smooth surfaces atoms arranged in a 3.8 Å square lattice could be resolved. We observed a tunneling-induced etching effect leading to an etch pit on the surface. Furthermore, by applying voltage pulses with amplitude > 5.0 V and duration > 100 μs holes with diameters of ∼ 150 nm could be produced. Scanning tunneling spectroscopic measurements were performed yielding I-V and ln I-s characteristics. The extremely small effective barrier height of ϕ = 0.3 eV inferred from d ln I/ds may be caused by dirt between the surface and the tip.