Twenty European domestic cats were each infected with 15,000 protoscoleces of Echinococcus multilocularis extracted from metacestodes grown in experimentally infected common voles (Microtus arvalis). Sixteen days after infection, ten cats were treated with a broad-spectrum anthelmintic and acaricide comprising praziquantel and milbemycin oxime. Five days later treated and untreated cats were euthanized and the intestine examined for E. multilocularis. Five of ten untreated cats were infected with E. multilocularis with worm burdens ranging from 235 to 1920 worms per cat. No E. multilocularis were recovered from any of the treated cats. This study has demonstrated that this new combination broad spectrum anthelmintic and acaricide for cats is highly efficacious against E. multilocularis and the relevance of this is discussed.