Fil: Malandrini, Jorge Bruno. Universidad Nacional de Catamarca. Facultad de Ciencias de la Salud; Argentina.Fil: Carnevale, Silvana. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Enfermedades Infecciosas. Departamento de Parasitología; Argentina.Fil: Soria, Claudia Cecilia. Universidad Nacional de Catamarca. Facultad de Ciencias de la Salud; Argentina.Fil: Velásquez, Jorge Néstor. Hospital Municipal de Infecciosas Dr. Francisco Javier Muñiz; Argentina.Fil: Paladino, M. Instituto Municipal de Zoonosis Luis Pasteur; Argentina.Fasciolosis is an alimentary zoonotic caused by Fasciola hepatica (unca or uncaca), a parasite that causes hepatobiliary disease with relative absence of gastrointestinal symptoms. Humans can get sick by eating plants or contaminated water. It is difficult to diagnose in the invasive stage becausethere are not eggs in feces. The need for count on diagnostic techniques with greater sensitivity and specificity is needed both for the clinic to determine endemic areas. Serological methods are useful in acute cases or as a screening test. Although fasciolosis is acquired at all ages, those most affected are children and lower of 19 ages groups have the highest rates of infection. The aim of this study was to determine the seroprevalence of fasciolosis in children and adolescents from Fiambalá Valley. There were collected serum samples from 77 children during the month of December 2009, in the town of Taton. They all agreed with their parents´written consent for evaluation. Thirty three serums were male and 44 female. Serum samples from children tested by ELISA for the detection of circulating IgG antibodies, revealed 44/77 (51,94 %) were positive. Twenty were females and 20 males. There was no significant difference by sex. The results show that the presence of fasciolosis should be considered as a disease of public health importance. Early detection should be a priority in control programs. The percentage of Fasciola hepatica infection found shows that Fiambalá valley is an endemic area for the different pathologies and requires strong educational intervention for prevention.