A total of 688 fecal and stool samples were collected from calves, lambs and children through out all seasons of the year including: 248 (62/ season) fecal samples of pre-weaned calves collected from diarrheic and apparently healthy animals from individually owned animals attending the veterinarian clinics in rural areas of Alexandria and Behera Provinces, 200 (50/ season) fecal samples of pre-weaned lambs were collected from diarrheic lambs and 240 (60/ season) stool samples were collected from children under 6 years old (the age of school entry) attending pediatric hospitals in Alexandria and Behera Provinces during the period extended from December 2008 to November 2009. All collected samples were subjected to microscopical examination by using Modified Ziehl-Neelsen (MZN) staining technique for detection of Cryptosporidium parvum oocysts. More over, all positive samples were confirmed by using RIDASCREEN Cryptosporidium ELISA kits supplied by GmbH, Darmstadt, Germany. It was found that the overall percentage of C. parvum infection in fecal samples of calves, lambs and children was 9.3, 13.5 and 11.7 %, respectively and the incidence of     C. parvum was higher in Behera Province than in Alexandria Province due to its rural nature. The effects of age, health condition and season of the year on the incidence of infection with C. parvum were studied and the public health significance of cryptosporidiosis was discussed.