In recent years, increases in the urban fox population have been observed in many countries of the Northern Hemisphere. As a result, Echinococcus multilocularis has entered the urban environment. Because of a possible increased risk for alveolar echinococcosis, intervention strategies need to be evaluated. In Zürich, Switzerland, 50 praziquantel-containing baits per km2 were distributed monthly in six 1-km2 bait areas and one 6-km2 bait area from April 2000 through October 2001. The proportion of E. multilocularis coproantigen–positive fox fecal samples collected remained unchanged in six control areas but decreased significantly in the 1-km2 bait areas (from 38.6% to 5.5%) and in the 6-km2 bait area (from 66.7% to 1.8%). E. multilocularis prevalence in the intermediate host Arvicola terrestris also decreased significantly in baited areas. This controlled baiting study shows that a pronounced reduction of E. multilocularis egg contamination is feasible in urban areas where the organism is highly endemic.