Abstract : Opisthorchiasis is a parasitic disease having natural foci. A number of body’s systems are involved in the pathological process of opisthorchiasis, including hepatobiliary system and gastro-intestinal tract – stomach, duodenum, and pancreas. The aim of this study was to assess clinical and laboratory parameters of patients with chronic opisthorchiasis who received anti-parasitic therapy with “Sausalin” (study group) in comparison with “Praziquantel” (control group). In total, this study included 143 patients with chronic opisthorchiasis, of which 100 composed the study group and the rest composed the control group. Those patients who were treated with “Sausalin” had reduction of pain localizing in the right hypochondrium (from 62.0% before therapy to 22 % after therapy). Such clinical phenomena as nausea, vomiting, decreased appetite, loose stools, and constipation diminished in every second patient presenting with these symptoms before the treatment with “Sausalin”. At the same time, individuals from the control group demonstrated significant improvement in general well-being, which manifested as improved appetite that was obvious in 46.5 % individuals before therapy and in 37.2 % individuals after therapy. In general, this study demonstrated more pronounced positive clinical dynamics in the course of antiparasitic therapy with “Sausalin” as compared to “Praziquantel"