This study was outlined to declare the effect of releases of Stethorus gilvifrons (Muls.) adults at different predator: prey ratios (P: p) to control the two-spotted red spider mite, Tetranychus urticae Koch on soybean plants under field cage conditions during summer season of 2007.  Effective control of T. urticae was gained after nine day from introducing the adult of the coccinellid predator when the P: p ratio was 1:10 or 1:20. Meanwhile at higher ratios (1:40 and 1: 50), the two-spotted red spider mite numbers were decreased after 12 days from the release. The numbers of the two-spotted red spider mite were decreased by 85 and 79.75% at 1:10 and 1:20 P: p ratios, respectively when adults of the coccinelld released. The number of the two-spotted red spider mite remained zero for a period of 12 days after the release. At the predator: prey ratio of 1:40, the reduction percentage of the two-spotted red spider mite was 10.13 and 40.37% after one and three days. Whereas, at the higher ratios 1:50 the reduction percentage was 8.5 and 32.0, 51.4, 67.2 and 86.70% after one , three, six, nine and 12 days from the release, respectively. After nine days from release P: p of 1:10, 1:20, 1:30, 1:40 and 1:50, the reduction percentage was 85.0, 79.75, 76.87, 76.33 and 67.20 %. After 12 days where as the reduction percentages were 100,100, 92.33, 91.75 and 86.7, respectively. The reduction rate was increased with lower P: p ratios and vice versa