Five macaque monkeys, three Macaca fascicularis, one M. fuscata, and one M. cyclopis were inoculated orally with 120 metacercariae of Paragonimus westermani and they were necropsied 70 to 400 days after infection. None of the infected monkeys became ill or manifested apparent clinical signs of paragonimiasis, although all the animals examined showed marked peripheral blood eosinophilia. The eosinophilia appeared soon after inoculation, reached peak by the 5th or 7th week, remained on a high level for about ten weeks, and thereafter declined gradually. The recovery of the inoculated metacercariae varied from 35.0 to 51.7%, with an average of 44.2%. All worms recovered were on the youngest developmental stage and 93.2% (88.1 to 100%) of them apparently remained in a slightly developed state in the skeletal muscles, irrespective of the species of the monkey. These flukes of the youngest stage recovered from the muscles of monkeys were infective for cats and 74.3% (60.0 to 90.0%) of the worms given orally developed into mature adults capable of producing normal eggs in the feces of the recipient cats 41 to 66 days after transfer. Thus, it was found that the three species of macaques were the paratenic host of P. westermani under laboratory conditions. The gross lesions which might be attributable to migration of immature P. westermani and the histopathologic findings in the experimental monkeys are described and illustrated.