Febrile patients in whom a parasitic etiology is suspected can be classified broadly into two categories for the purpose of diagnostic evaluation based on the presence or absence of accompanying eosinophilia. Generally, the absence of eosinophilia indicates a protozoan etiology while the presence of eosinophilia is associated with tissue-invasive helminthic infections. The history and physical examination often points to a specific diagnosis that can be confirmed by appropriate laboratory tests.