The aim of the present study was to determine the efficacy of 5-chloro-2-methylthio-6-(1-naphthyloxy)-ih-benzimidazole called compound alpha and compared to two other commercial fasciolicides through the percentage of F. hepatica egg-reduction in cattle. 40 Holstein-Friesian adult cows previously determined to be positive in fluke eggs by sedimentation were used. The cows were divided in 4 groups (G) of 10 animals each, and were treated with the corresponding drug on day 0.