OBJECTIVE To evaluate the efficacy of tribendimidine (TBD) against 3 geographical isolates of Trichinella spiralis in mice. METHODS Isolates of T. spiralis from Henan (hereinafter referred to as HnT.s), Yunnan (referred to as YnT.s) and Heilongjiang (referred to as HIjT.s) were used in the study. 144 Kunming strain mice were divided into 2 groups: 72 mice in group A (adult stage, treatment at 5 d after infection), and 72 mice in group B (encapsulated larva stage, treatment at 53 d after infection). Group A was further divided equally into 12 sub-groups. Mice in every 3 sub-groups were each infected orally with 200 T. spiralis larvae of the 3 isolates respectively, and the remained 3 subgroups served as untreated control. Mice in the 3 sub-groups infected with one isolate were orally treated with TBD at a single dose of 10, 20, and 30 mg/kg, respectively. Group B was treated as group A but with a course of TBD once daily at a dose of 100, 200, and 300 mg/(kg x d) for 7 d, respectively. Mice in group A were sacrificed 2 d post-treatment and adult worms were recovered from the small intestine and counted. Those in group B were sacrificed 10 d after completion of 7 d treatment. The intact diaphragm was removed and digested for collecting larvae. Worm burden and worm reduction of each treated sub-group were calculated and statistically compared with the respective control. RESULTS In group A, the mean worm burden in the treated sub-groups infected with HnT.s and YnT.s were all significantly lower than that of the controls (P < 0.01), with a mean worm reduction rate of 39.0%, 57.9%, and 86.0% in HnT.s sub-groups, and of 34.9%, 69.3%, and 92.2% in YnT.s sub-groups, respectively, showing an increase with the dosage, 2 mice in each of the 30mg/kg sub-groups were cured. The worm burden in the 10 mg/kg of HljT.s subgroup was similar to that of the control (P > 0.05), but was significantly lower in the other 2 sub-groups than that of the controls (P < 0.01). The worm reduction rate in the 3 sub-groups was 27.9%, 57.4%, and 60.7%, respectively. In all treated sub-groups of group B, the mean worm burden was significantly lower than that of the controls (P < 0.05), with a mean worm reduction rate of 57.8%, 75.4%, and 87.5% in HnT.s sub-groups, of 74.5%, 92.4%, and 99.1% in YnT.s sub-groups, and of 50.5%, 53.3%, and 61.6% in HljT.s sub-groups, respectively, with the 3 dosages. CONCLUSIONS Tribendimidine shows adequate efficacy on Trichinella spiralis adults and on encapsulated larvae of the 3 geographical isolates in mice, with better effect on Yunnan isolate.