The clinical consequences of tapeworm infection in humans depend on whether the patient serves as the primary or the intermediate host. In the former case, the adult worm is confined to the lumen of the gut, and the consequences of the infection are typically mi-nor. Taeniasis saginata and diphyllobothriasis are prime examples. In contrast, when the patient serves as the intermediate host (eg, for E. granulosus), larval development pro-duces tissue invasion and frequently serious disease. The capacity of H. nana and T.solium to use humans as both primary and intermediate hosts is unique.