The outer cysts (Oc) of Fasciola gigantica metacercariae (Mc) were separated in an aqueous two-phase system composed of polyethylene glycol and dextran in distilled water. A large number of separated Mc without Oc were recovered in the bottom layer rich in dextran in the system. Ten separated Mc in the layer were used to inoculate the mouse with a syringe and juveniles were recovered from the animals on the 14th day. When the number of juveniles recovered was compared with that from the mice infected orally with the same number of Mc, there was a significant difference between them (P < 0.05). The former method is easier than the latter for inoculation.