Epitaxial CeO2buffer layers and YBa2Cu3O7−&dgr;thin films have been growninsituon (11¯02) sapphire by electron beam evaporation. Buffer layers of only 20 nm thickness inhibit interdiffusion between YBa2Cu3O7−&dgr;and Al2O3as determined by depth profiling using x‐ray photoelectron spectroscopy. The layers show smooth surfaces and narrow interfaces. High lattice perfection of the CeO2layer has been shown by x‐ray diffraction. Laue oscillations up to ninth order have been observed in thin CeO2buffer layers on sapphire. We found only one epitaxial orientation with YBa2Cu3O7−&dgr;(001) ∥ CeO2(001) ∥ Al2O3(11¯02) and YBa2Cu3O7−&dgr;[110] ∥ CeO2[100] ∥ Al2O3[112¯0]. YBa2Cu3O7−&dgr;films grown on these buffer layers revealTc=88±0.5 K, &rgr;(300 K)=380 &mgr;&OHgr; cm, andjc(77 K, 0 T)=1.3×106A/cm2.