We report ellipsometric measurements from surfaces of three single-crystal samples of YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}}. Two of the samples were untwinned with {ital T}{sub {ital c}}=90 and 66 K. The third sample was a tetragonal single crystal with low oxygen content ({delta}{similar to}0.9). We used solutions for {var epsilon}{sup {ital c}} obtained from measurements on two faces of thick, single-crystal, twinned samples to solve for the other two components of the dielectric tensor ({var epsilon}{sup {ital a}} and {var epsilon}{sup {ital b}}). We examine anisotropy in the {ital ab} {ital plane} and observe unexplained polarization of several peaks, in the middle range of oxygen content. Most notably, we observe a {ital b}-polarized feature at 4.16 eV and an {ital a}-polarized feature at 4.59 eV for {ital T}{sub {ital c}}=66 K, which we propose to be a splitting of the 4.03-eV peak observed in the insulator.