A total of 807 stool and fecal samples (251 stool samples from diarrheic children under six years old, 254, and 250 fecal samples from diarrheic and apparently healthy pre-weaned calves and lambs, respectively in addition to 50 fecal samples from dogs) were collected from different localities in Behera and Menoufia Governorates for detection of Cryptospridium spp., Giardia spp. and Entamoeba histolytica). Cryptosporidium spp. has been detected by using modified Ziel-Nelssen Stain (MZN) in 30 (11.95%); 26 (10.24%); 31(12.4%) and 2(3.84%) of the examined stool and fecal samples from children, calves, lambs and dogs, respectively in both Governorates. There were significant relationships between infection of the examined calves with Cryptospordium parvum and their age and healthy status. The same relation was noticed in concern with the examined children. Results of MZN were confirmed by using ELISA which was found sensitive (overall sensitivity 96.6%). In spite of the higher sensitivity of PCR than MZN for detection of C. parvum in fecal specimens especially when oocysts are scanty, the high cost of reagents and lack of expensive instruments which are not available in all clinical laboratories render MZN staining technique acceptable and reliable. By using direct smear and formal ether method, Giardia intestinals has been detected in {27(10.75%); 51(20.08%); 63(29.2%) and 5 (9.61%)} of stool and fecal samples from the examined children, calves, lambs and dogs, respectively from both Governorates. Calves, lambs and dogs seem to be important sources for Giardia intestinalis to man. Entamoeba histolytica has been detected in {19(7.56%); 0 (0),0(0) and 2(3.84%) of stool and fecal samples of the examined children, calves, lambs and dogs, respectively in both governorates. Dogs are regarded as an important source of Entamoeba histolytica to man.