The article provides data on the study of acute and chronic toxicity of the new anthelmintic compound «K-55». For the acute experiment in rats, the following doses for single intragastric administration were determined: 50 mg/kg, 300 mg/kg, 500 mg/kg, 700 mg/kg, 1000 mg/kg and 2000 mg/kg. In studies of chronic toxicity of a new compound, animals of the first group received 1/10 of the maximum administered dose of the compound (200 mg/kg), the second - 1/20 (100 mg/kg), the third dose was approached to therapeutic one (20 mg/kg). In rats of the experimental group that received the compound at a dose of 200 mg/kg, a decrease in the number of erythrocytes by 25.3 %, leukocytes by 41.7 % at p ≤ 0.05, monocytes by 28.9 %, lymphocytes by 6.9 % was noted and the level of hemoglobin by 5.4 %. As well as an increase in the number of platelets by 30.5 % at p ≤ 0.05 and segmented neutrophils by 36.7 %. But the differences to the control values were not significant. It has been established that this agent, according to the parameters of acute toxicity, belongs to the 3rd hazard category (moderately hazardous substances) according to GOST 12.1.007-76 «Classification and general safety requirements». Thus, the compound «K-55» can be used for clinical trials on animals and be approved for production.