These sutdies were conducted to investigate the joint toxic action of mixtures of several acaricides including amitraz, bifenthrin, propargite, fenbutatin dxide and bxide dicofol to the field-collected strian of Tetranychus urticae. The synergistic action of acaricidal mixtures was greatly varied with the kind of acaricide combinations and their mixture ratios. The combinations of amitraz with each of the tested acaricides were synergized at the given mixture ratios. The higher synergistic action in the each combination was observed at 2 : 8 ratio of amitraz and bifenthrin, 8 : 2 ratio of amitraz and fenbutatin oxide, 4 : 6 ratio of amitraz and propargite and 6 : 4 ratio of amitraz and dicofol.