Heteroepitaxial multilayers of YBa2Cu3Ox/PrBa2Cu3Ox/YBa2Cu3Ox have been made by sputtering. Typical thicknesses of the individual layers are of the order of 50 nm. No degradation of the transition temperature and the critical current density due to the presence of the PrBa2Cu3Ox layer could be observed. By using High Resolution Transmission Electron Microscopy the atomic details of the interfaces and the defect structures have been studied. These films showed a perfectly stacked lattice just above the interface between film and substrate. The orientation of the c-axis perpendicular to the substrate was fairly perfect. The structural faults are mainly distributed in the middle and overlying layers. The dominant defects in our films seems to be stacking faults which give rise to nano-sized coherent anti-phase domains with the 1-2-3 structure.