Between July 2005 and June 2006, a case-control study was carried out to identify risk factors for hydatidosis in Lima, Peru. As a result, 32 cases were matched according to age, sex and birthplace in 64 controls. The participants were interviewed using a questionnaire designed to evaluate environmental and behavior factors associated to hydatidosis. By using Multiple Conditional Logistic Regression, it was determined that the owners of >or=10 dogs in a rural area (aOR=8.7; 95% Cl=1.3-57.5) and those raising sheep (aOR=5.9; 95% Cl=1.2-28.1) were independently related to a higher risk of hydatidosis. The belief that food may transmit hydatidosis (aOR=0.1; 95% Cl=0.01-0.7) and the activity of raising goats (aOR=0.02; 95% Cl=0.001-0.6) were inversely associated to hydatidosis. Preventive measures to reduce the transmission of hydatidosis to human beings in endemic areas in Peru require: limiting the number of dogs kept in each household, regularly controlling parasites and preventing access of dogs to human food and drinking water; all of this in addition to educational campaigns to change the practices that lead to the transmission of hydatidosis.