There was studied an effectiveness of the new anthelmintic drug Supramil® tablets for prevention of dirofilariasis in dogs. With a monthly treatment of dogs free from larvae of Dirofilaria spp. with the drug Supramil® tablets, used at dose of 0.5 mg / kg on a body weight according to milbemycin oxime, in a region unfavorable for dirofilariasis, the preventive effectiveness of the drug was 100 %. Monthly control of microfilariaemia, carried out before each drug treatment, showed an absence of larvae of Dirofilaria spp. in peripheral blood of 100% of experimental animals, which indicates not only high preventive efficacy of the drug, but also its prolonged microfilaricidal action and a possibility to use it for prevention of dirofilariasis with an interval of 28…35 days. Thus, Supramil® tablets are highly effective to prevent dirofilariasis in disadvantaged regions.