Zinc oxide (ZnO) films were deposited on (1 1 (2) over bar 0) or (0 0 0 1) oriented sapphire substrates heated up to 800 degreesC with a radio frequency (rf) power ranging from 40 to 200 W at an argon gas pressure range 0.08-11.7 Pa by rf magnetron sputtering from a ZnO target, and the dependence of structural properties of these films on the preparation conditions was studied by using XRD, RHEED, SEM and AFM. The results obtained by XRD and RHEED measurements showed that films deposited on sapphire (1 1 (2) over bar 0) plane were (0 0 0 1) oriented heteroepitaxially,grown films of mosaic structure independently of the deposition conditions and the crystallinity of films was improved with increase in film thickness and substrate temperature, and that most of the films grown on sapphire (0 0 0 1) plane consisted of (0 0 0 1) oriented fiber-texture crystallites, the degree of whose a-axis ordering was changed depending on the deposition conditions.