High conductive, transparent films of Cd-Sn oxide have been prepared by dc diode reactive sputtering of Cd-Sn alloys in Ar-O_2 mixtures. Alloy targets (Cd/Sn atomic ratio of 2 : 1) were utilized. Experiments have been carried out under the following conditions. The ratio of Ar/O_2 and the total pressure of gas mixture were ranged from 9/1 to 4/1,and from 1×(10)^<-2> to 6×(10)^<-2> Torr, respectively. The dc applied voltage was in the range of 1&acd