Coprological studies of school children from four communities in the Northern Bolivian Altiplano were carried out in order to estimate the prevalences and intensities of Fasciola hepatica infection. Single stool specimens were collected at random from 558 school children (308 boys and 250 girls) aged 5-19 years old. Nineteen different parasite species (13 protozoan and six helminths) were detected. Of the children examined, 98.7% (96.5-100%) presented infection with at least one parasite species. The mean prevalence of 27.6% by Fasciola hepatica (range, 5.9-38.2%) was the highest not only with respect to the helminth species found in the Northern Bolivian Altiplano but also among the fasciolosis prevalences reported in children in other parts of the world to date. Prevalences were significantly different among the communities surveyed and was significantly higher in the 9-12 years age group. There were, however, no significant differences between sexes. Among the 154 children presenting F. hepatica eggs in stools, intensities ranged from 24-5064 eggs per gram of faeces (epg), with arithmetic and geometric means of 474 and 201 epg, respectively. Significant differences in mean egg output were detected between communities, sexes and age groups. Individual fasciolosis infections coexisting with other pathogenic parasite species (Entamoeba histolytica and/or E. dispar, Giardia intestinalis, Balantidium coli, Dientamoeba fragilis, Cryptosporidium sp., Hymenolepis nana, Taenia spp., Trichuris trichiura, Ascaris lumbricoides and Enterobius vermicularis) were detected. A significant positive association with F. hepatica was only found in the case of G. intestinalis. This coprological study not only verifies the existence of high prevalences of F. hepatica among humans in the Northern Bolivian Altiplano, but also demonstrates the need to expand the Southern boundaries of this high endemic zone to include the Southeastern region of Lake Titicaca.