With the objective of knowing adequately the spectrum of activity of albendazole against intestinal helminthiases, we made observations regarding hymenolepiasis caused by Hymenolepis nana. Two series of investigations were carried out: a) treatment of mice with single doses of either 25 or 50 mg/kg, repeated after ten days, using as controls animals treated with 25 mg/kg of praziquantel or not treated with any antiparasitic drugs; b) treatment of adults and children with 400 mg daily for three consecutive days, repeated after ten days. The observations in animals have shown a lack of efficacy of albendazole, since persistence of live worms in the intestine was verified systematically. On the other hand, only 10% of the treated patients could be considered cured. Therefore, according to the procedures here described, this antiparasitic agent could not satisfactorily treat hymenolepiasis.