Critical field and critical current density measurements performed on single crystals of Y1Ba2Cu3O7-x demonstrate that its superconducting properties are those of a conventional superconductor with uniaxial ansiotropy. The high temperature upper critical field anisotropy is temperature independent except very near Tc, and in the best crystal had a value of 7:1. The anisotropy in the critical current density is larger than this, particularly at high fields and high temperatures. The critical field data is generally well described by anisotropic Ginzburg-Landau theory which is used to calculate the coherence lengths and other parameters describing the superconductivity. © 1987.