Chagas' disease is an emerging public health problem in areas where the disease is not endemic. Treatment with benznidazole has shown efficacy in the acute stage of the disease, but its efficacy in the chronic stage remains controversial, and unwanted side effects are more frequent and severe in adults than in children. This study describes the profile of side effects of benznidazole in a cohort of Trypanosoma cruzi-infected patients in a European country.