The chemico-therapeutical activity of albendasol was studied on 45 guinea-pigs experimentally invaded by 500 muscle trichinellae. The experimental animals were treated with the preparation on the 30th, 60th and 90th day post invasion. At the 10 mg/kg dose a 96.4% effectiveness against 30 day muscle trichinellae, 95.2% against the 60 day, and 81.2% against the 90 day trichinellae was scored, while at 20 mg/kg dose the effectiveness of the treatment was respectively 97.1, 96.3 and 88.6%. Pathomorphological and enzyme (alkaline and acid phosphatase) changes indicate that albendasol probably inactivates the inflammatory protective mechanism of the microorganism and directly participates in the parasite's cell metabolism.