Abstract:The ultrastructural characteristics of the adult tegument in Metorchis orientalis obtained cats experimentally infected with metacercariae of this worm was observed with scanning electron microscopy on the back and belly of the worm.The trematod of cuticular spines was observed to be covered on the tegument.The arrangement of the cuticular spines revealed regularly tilted rows,and their intervals between the rows were densely covered to sparse gradually from the anterior to posterior part of the body.These cuticular spines was found to belong to a mixed type and the rows of the cuticular spines were in groups.The sensory organs could be divided into 4 types,including non-ciliated,round-mound big papillae and big,middle and small papillae with cilia.The epidermis patterns showed some variations from different parts of the tegument,and the characteristics on the anterior of tegument was found to be most predominant.It is evident that the ultrastructural characteristics of the tegument of M.orientalis may be related to the adaptation to its parasitism in the host and also have significance on taxonomy.