The index of natural infection and the density of porasitism in crabs collected in three provinces of the Deportament of Cajamorca, Perú, have been studied, and they hove revealed that metacercariae of Paragonimus Braun, 1899 are found in 43.97 [%] of 539 specimens of Pseudothelphusa chilensis, Milne Edwards, 1843, the unique crab found in the zone. The parasited orgon was almost exclusively the hepatopancreas overaging 10.33 metacercarias per crab. The odult specimens which were inoculated with metacercariae were identified as Porogonimus peruvianus Miyozoki, Mirando and Ibáñez, 1969, with the exception of three samples wich belonging to the species Paragonimu ealiensis Little, 1968.