The flukes were collected from the rumen of infected cows (Bos indicus) from slaughterhouses in Mueang district, Chiang Mai province and Mueang district, Lamphun province between January and March 2000. After opening the rumen of cow, the flukes were removed and washed three times with 0.85% sodium chloride solution. Some were mounted whole and sagittal paraffin sections were obtained for identification; the remainer were kept at -20 °C for DNA extraction. The metacercarial stage of Stellantchasmus falcatus, obtained from the naturally infected half-beaked fish (Dermogenus pusillus), was used as an outgroup in this tests.