This study was performed to observe the susceptibility of dogs and cats as definitive hosts of Paragonimus ilektsuenensis. The metacercariae of this luke were obtained from Sesarma dehaani collected at a focus near the mouth of Sumjin river in November, 1986 and February, 1987. The larvae isolated from the crabs were introduced Per os into 7 albino rats, 2 dogs and 3 cats. The adults were recovered from the experimental animals, End they were morphologically observed and measured. The results were as follows: 1. The recovery rate of adult worms at 42 days after infection was 53.3% from three albino rats, 21.0% from a dog and 12.7% from two cats. Most of the worms were recovered from the worm capsules in the lungs. 2. The size of worms recovered from albino rats, a dog, and cats 42 days after infection aver-aged $6.3{ imes}3.2mm,{;}6.3{ imes}3.0mm,{;}or{;}6.2{ imes}3.5mm$, respectively. There were little differences in the morphology of worms by different experimental animals. 3. The size of eggs from a dog was $88.9{ imes}49.3{mu extrm{m}}$, and that from cats was $84.3{ imes}53.7{mu extrm{m}}$ on average. Dogs and cats were good definitive hosts of p. iloktsuenensis. This fact suggests that human infection by this luke may be possible if the metacercariae were ingested.