Water samples were collected different water sources and different districts of Dakahlia G., from September 2005 to August 2006, were investigated for pathogenic protozoa. Water specimens were examined by concentration technique followed by modified Ziehl-Neelsen (MZN) and Truant auramine-rhodamine (AR) stains for Giardia sp. cysts, Cryptosporidium sp. oocysts, and other protozoa species. In the 1st survey, 94/480 (19.6%) water samples had protozoa. Prevalence rates were in summer 38/120 (31.6%), autumn 27/ 120 (22.5%), spring 20/ 120 (16.6%) and lastly winter 9/120 (7.5%). Protozoa were less common in treated potable water tanks 15/120 (12.5%), followed by River Nile (Demiatta branch) 22/120 (18.3%) and sub-branch Bahr-El-Saghear 24/120 (20%). The highest prevalence was in water of the main local draining 33/120 (27.5%). In the 2nd survey, 840 potable water samples from seven districts were examined. Prevalence in descending order was C. parvum (3.1%), G. intestinalis (2.1%), E. histolytica (1%), Blastocystis homi-nis (1%), Iodamoeba sp, (0.5%), Isospora belli (0.47%), E. coli (0.36%), Cyclospora cayetanensis (0.24%), and Chilomastix mesnilli (0.12%). Data suggested that C. parvum and G. intestinalis were the commonest disease-agent. The implementation of preventive measures to protect water system from protozoa contamination was given.