Searching for Cryptosporidium sp., we examined (throughout a year) 300 samples of feces belonging to 210 diarrheic children assisted at the Hospital Provincial del Centenario. Their ages ranged from a week to thirteen years, though most of them were not older than three years. Feces were collected in 10% formol, enriched by the formol-ether method and stained with safranine 1% and modified Ziehl Neelsen permanent techniques. Cryptosporidium oocysts were detected in 16 out of the 210 children examined (7.6%). The number of oocysts in positive samples was from moderate to abundant, with the exception of one child who showed a very low number of oocysts. Additional samples of only 5 out of these 16 children were obtained. In 3 of them the sample became negative. In none of the positive patients, trophozoites, cysts, sporocysts, eggs or any other enteroparasite larvae were simultaneously detected. The search for Cryptosporidium sp. in diarrheic children should be considered a parasitological routine for a differential etiological diagnosis.