Introduction. Helminthic infestation in horses is one of the most important problems the veterinary specialists face today, because helminth end-products affect significantly the overall condition of animals. The weight loss, depression, impaired work capacity, deterioration of stamina, exterior characteristics and natural resistance are observed and all together create the favourable conditions for arising the diseases of various etiology and cause considerable damage to horse breeding industry. The aim of the research is to determine the therapeutic efficacy of the anthelminthic drug «Bimectin®» against the intestinal helminthiasis in horses in the Tyumen region conditions.Materials and Methods. The studies were carried out with regard to the clinical examinations of animals and in compliance with the generally accepted parasitological methods. The infestation intensity (II), extensive efficacy (EE) and intensive efficacy (IE) were assessed, the haematological and biochemical blood tests were made on the 7th and 14th day before and after applying the drug. The results were statistically processed using the Statistica 6.1 software.Results. When assessing the therapeutic efficacy, we have determined that at a single application in the dose of 1.13 g. per 100 kg. of animal weight, the anthelminthic drug «Bimectin®» turned out to be 100 % therapeutically efficient and well tolerated by horses infested with Oxyuris equi and suborder Strongylata helminths, 91.7 % efficient against Parascaris equorum and 83.3 % efficient against Strongyloides westeri helminths.Discussion and Conclusions. Thus, in the result of assessing the therapeutic efficacy of the anthelmintic drug «Bimectin» against the horse helminthiasis, its economic benefit for using at the horse breeding farms of the region was confirmed, which should be taken into account when planning the combat measures against the nematode infestation in horses.