The new drug niclofolan (bayer 9015, Bilevon), 5,5'-dichloro-2,2'-dihydroxy-3, 3'-dinitrobiphenyl, has been used in the treatment of Paragonimus westermani in dogs and cats and P. iloktsuenensis in rats. It was proved that administration of daily dose of 1.0 mg/kg body weight for 3 days or in 2 doses of 2.0 mg/kg body weight by alternate days were evidently effective for the infected dogs, cats and rats with the lung flukes, and toxic manifestations were not found.