Abstract: The karyotypes of diploid and triploid forms of the common liver fluke were analysed by air-drying method.The chromosome number of diploid form was 2n = 20,n=10, and the karyotype consists of the chromosomes with 2M, 4Sm, 3St, 1T. There were a number of similarities between the karyotypes of diploid form and triploid iorm except that the chromosome number of the triploid was 3n = 30 and n = 10. Judging from the shape of adult worms and their life cycle, the worm of the diploid form is similar to F, gigontica while the worm of the triploid form is similar to F. hepatita.In several specimens of the triploid worms there were some cells having 20 chromosomes that were composed of 10 monovalent chromosomes asd 10 divalent chromosomes. This kind of cell, in a group of 8 cells, was primary spermatocyte. According to the measurement, these chromosomes could be classified into 10 pairs and each pair was made up by one monovalent chromosome and one divalent chromosome. The karyotype of these chromosomes was similar to that of the triploid form. It is a rare phenomenon that one set of monovalent chromosomes and one set of divalent chromosomes co-exist during the same metaphasc (Figs. 1-4).