Recent studies on high Tc superconducting oxide films are reviewed with special emphasis on the preparation by sputtering. Comparison and analysis are made on various p reparation methods to point out key factors and problems which must be taken into account for the film synthesis. Some experimental details and results are presented with respect to the preparation of La-Sr-Cu-0 and Yb-Ba-Cu-0 films by 50 Hz ac sputtering in which we observed some features characteristic to the film preparation on ceramic substrates. Epitaxial growth of single crystal Y- Ba-Cu-O films is also noted, since the anisotropic and high critical current density of the films is quite important not o nly for the application to electronic devices but also for the mechanistic studies of su percond tic t i vi t y .