The purpose of the research is to evaluate the acaricidal activity of the antiparasitic agent Meradok against demodicosis in cattle. Materials and methods. Acaricidal activity against demodex mites in cattle was studied from 2024 to 2025 on 50 Black and White cattle (heifers aged 11–12 months). Five groups of 10 animals were formed from matched animals: four experimental groups and one control group. Meradok was administered subcutaneously to test animals in the neck area, clipping the hair. The injection site was treated with ethyl alcohol: Group 1 received 0.25 ml/50 kg, Group 2 – 0.5 ml/50 kg, Group 3 – 0.75 ml/50 kg, and Group 4 – 1 ml/50 kg, twice, 7 days apart. The control group of animals did not receive the drug. The results were statistically processed using Statistica 6.1 and Microsoft Excel. Results and discussion. Meradok has an 87.6% therapeutic efficacy for demodicosis in cattle when administered subcutaneously at a dose of 1.0 ml/50 kg twice, 7 days apart. To prevent recurrence of demodicosis, it is necessary to treat the entire herd, as well as the premises, equipment, and care items. Daily grazing of cattle for sun exposure is essential, and animals must be cleaned daily. The microclimate of animal housing facilities must comply with zoohygienic standards.