The effect of the optical anisotropy of the high temperature superconducting compound YB2Cu3O7-x (YBCO) on spectroscopic ellipsometry (SE) measurements was studied. For this, the method of spectroscopic anisotropy micro-ellipsometry (SAME) was employed on c-axis- as well as on a,b-axes-oriented YBCO single crystals. SAME measures the ellipsometric parameters Delta and Psi as a function of the angle alpha which describes sample rotation around the surface normal. The analysis of the resulting Delta(alpha) and Psi(alpha)-curves yielded the ordinary and averaged extraordinary complex refractive indices in the UV-VIS range. Additionally, the crystallographic orientation angle phi between the optical axis and the surface normal could be determined. The single crystal results were applied to SE measurements performed on differently oriented YBCO thin films which were prepared by ion beam sputter deposition on top of (100) SrTiO3 substrates. It is shown that SE allows for in-situ monitoring of the crystallographic orientation of thin YBCO films.