A highly reproducible procedure for preparing films from ultrafine particles of metal oxides has been developed. The ultrafine particles of several tens of angstroms in size are grown by the evaporation of the metal in low oxgen gas pressure, and subsequently, the film is constructed from the ultrafine particles aligned in a specific direction on the substrate. The particles' size and film structure were studied under various deposition conditions, i.e., oxygen gas pressure, rf activation power, evaporation temperature, and others. The ultrafine particle films prepared with this procedure may serve as a highly sensitive gas sensor.