Studies were undertaken to evaluate by parasitological techniques the course of intestinal and muscular invasions in mice infected with Trichinella spiralis and treated with TFX-Thymomodulin (TFX-Th). Studies were conducted on 120 mice of BALB/c and SWISS strains, infected each with a mean invasive dose of 300 T. spiralis larvae. TFX-Th (Thymoorgan GmbH Pharmazie Co. KG, Vienenburg, Germany) was administered subcutaneously at 30 mg/kg body weight. Depending upon duration of TFX-Th administration and stages of intestinal and muscular invasions, three experiments were distinguished in the study. The results indicated that TFX-Th promoted eradication of larvae from muscles, whether administered at the early of the late stage of T. spiralis invasion