The inhibitory activity of mangiferin (50 mg/kg/die and 100 mg/kg/die) on Cryptosporidium parvum was evaluated in a neonatal mouse model and its activity was compared with that of paromomycin (100 mg/kg/die). At 4 days of age, neonatal Swiss conventional outbred mice were experimentally infected by oral administration of 10(4) oocysts/animal of C. parvum and treated orally for 10 consecutive days, starting 7 days after the experimental infection. One group of mice was left untreated. To evaluate the efficacy of mangiferin, from euthanised mice, 3-mum-thick tissue sections of the intestine were stained with haematoxylin-eosin and periodic acid Schiff. Immunohistochemistry was also used by employing a monoclonal anti-C. parvum antibody. Oocysts were counted and results were expressed as mean oocysts number/intestine. Results obtained show that mangiferin at 100 mg/kg/die has a significant anticryptosporidial activity and that its activity is similar to that showed by the same dose (100 mg/kg/die) of paromomycin. However, both mangiferin and paromomycin were not able to completely inhibit intestinal colonization of C. parvum but only to reduce it. This reduction was calculated at over 80% for both mangiferin and paromomycin with respect to the untreated control. A significant activity was found also for mangiferin at 50 mg/kg/die only after the end of treatment.