To evaluate the efficacy of a formulation with 0,5% of eprinomectin in cattle to control H. irritans, two trials were conducted for the control of H. irritans in the field in the state of Rio de Janeiro, using 0,5% of eprinomectin, at a dose rate of 500 mc g/kg body weight, corresponding to 10 mL/100 kg. The efficacies for days +7, +14, +21 e +28 after treatment were respectively 100%; 94,3%; 86,2% and 24,5% for the first study and 100%, 100%, 100%, and 0% for the second one.