We conducted a case-control study to clarify the risk factors for human fascioliasis in the Northern Peruvian Altiplano. Cases (n = 61) were individuals who were diagnosed as having chronic fascioliasis by faecal and/or serologic (Fas2-ELISA) studies. Controls (n = 61) had negative serologic and coprological results for Fasciola hepatica. We identified an association between fascioliasis and four variables (40 analysed): the habit of drinking alfalfa juice (OR = 4.5; 95% CI 1.8-11.1; P < 0.001); familiarity with aquatic plants (OR = 4.3; 95% CI 1.8-10.6; P < 0.001); dog ownership (OR = 5; 95% CI 1.7-15.1; P = 0.002); and raising more than five sheep (OR = 0.3; 95% CI 0.1-0.8; P = 0.01). According to clinical presentation and laboratory studies, dizzy spells (P = 0.01), history of jaundice (P = 0.01), peripheral eosinophilia (P = 0.005) and Ascaris lumbricoides in stools (P = 0.001) were associated with fascioliasis. The principal exposure factor for F. hepatica infection was drinking alfalfa juice. In conclusion, we suggest that human fascioliasis in Peru should be suspected in patients from livestock-rearing areas, who present with recurrent episodes of jaundice and who have a history of consumption of alfalfa juice or aquatic plants, or who have eosinophilia. © 2005 Royal Society of Tropical Medicine Hygiene. Published by Elsevier Ltd. All rights reserved.