Fascioliasis is a zoonotic disease emerging in numerous parts of the world. Fascioliasis is an important food-borne parasitic disease caused by the two trematode species, Fasciola hepatica and Fasciola gigantica. The characterisation and di erentiation of Fasciola populations is crucial to control the disease, given the di erent transmission, epidemiology and pathology characteristics of the two species. Furthermore, in any endemic area, the characterisation of scenarios and patterns of infection must always be considered the starting point before implementing any control measure. Morphometric analyses were made with a computer image analysis system (CIAS) applied on the basis of standardised measurements and the logistic model of the body growth and development of fasciolids in the different host groups. The speci c results have been grouped into three parts. A) The phenotypic features of fasciolid adults infecting bovines inhabiting Pakistan and Bangladesh have been studied to characterize fasciolid populations involved. Since it is the rst time that such a study has been performed, the results are compared to pure fasciolid populations, (i) F. hepatica from the European Mediterranean area (Spain and France) and (ii) F. gigantica from Burkina Faso, i.e. geographical areas where both species do not co-exist. Only parasites obtained from bovines were used. The multivariate analysis used showed that the characteristics of fasciolids from Pakistan and Bangladesh are between F. hepatica and F. gigantica standard populations. These results demonstrate the existence of fasciolid intermediate forms in the endemic area studied in Pakistan and Bangladesh, respectively.Fascioliasis is a zoonotic disease emerging in numerous parts of the world. Fascioliasis is an important food-borne parasitic disease caused by the two trematode species, Fasciola hepatica and Fasciola gigantica. The characterisation and di erentiation of Fasciola populations is crucial to control the disease, given the di erent transmission, epidemiology and pathology characteristics of the two species. Furthermore, in any endemic area, the characterisation of scenarios and patterns of infection must always be considered the starting point before implementing any control measure. Morphometric analyses were made with a computer image analysis system (CIAS) applied on the basis of standardised measurements and the logistic model of the body growth and development of fasciolids in the different host groups. The speci c results have been grouped into three parts. A) The phenotypic features of fasciolid adults infecting bovines inhabiting Pakistan and Bangladesh have been studied to characterize fasciolid populations involved. Since it is the rst time that such a study has been performed, the results are compared to pure fasciolid populations, (i) F. hepatica from the European Mediterranean area (Spain and France) and (ii) F. gigantica from Burkina Faso, i.e. geographical areas where both species do not co-exist. Only parasites obtained from bovines were used. The multivariate analysis used showed that the characteristics of fasciolids from Pakistan and Bangladesh are between F. hepatica and F. gigantica standard populations. These results demonstrate the existence of fasciolid intermediate forms in the endemic area studied in Pakistan and Bangladesh, respectively.