Thin films of YBCO were prepared using a mass-spectrometer controlled coevapora-tion/MBE process with atomic oxygen. Under the conditions of low pressure, necessary for mass-spectrometer rate control, it is shown that an atomic oxygen beam source can be utilized in order to grow high quality thin films of YBCO as well as multi-layer structures involving YBCO and Y2O3. Values of Tc = 88.5 K and Jc = 6–106 A/cm2 at 77 K were determined for a strip with a width of 10 μm of YBCO deposited on a LaAlO3 substrate. Film structure is analyzed by XRD and rocking curve measurements. Magnetic characterization of films and multi-layer structures are reported.