Giardia cysts and Cryptosporidium oocysts are (protozoan single cell) causative agent forrnmost of enteric diarrhea and resistant to most of disinfectants. The main purpose of thisrnresearch was to determine, enumerate and test viability of Giardia cyst and Cryptosporidiumrnoocysts in Addis Ababa municipal drinking water. A total of 115 samples were collected fromrndifferent sampling sites at source, reservoir, and public tap. A 100 liters of water collectedrnfrom each sample and a total of over 10,000 liters of water filtered, concentrated andrnexamined for identifying (oo)cysts. Detection of (oo)cysts in water sample was conductedrnusing (USEPA Method 1623) Aqua-Gloâ„¢ G/C Direct Comprehensive Kit (Waterborne â„¢,rnInc.) fluorescein-labeled monoclonal antibody for Simultaneous Direct Immunofluorescencerndetection of Giardia cysts and Cryptosporidium oocysts. Giardia detected at source 33.3%,rnreservoirs 5.88%, and public tap 12.5%. Likewise Crypto was found at source, reservoirs, andrnpublic tap 55.6%, 8.82%, and 18.06% respectively. The mean concentration of Giardia andrnCrypto ranges from 5 to 0.15 and 9.89 to 0.5 respectively. The viability test demonstrated allrnthe (oo)cysts collected was nonviable except at source (untreated water) (DAP-PI+). This canrnbe due to the age of the (oo)cysts, long distance source of contamination, sporulation of thern(oo)cyst before maturation with the combination of the disinfectants used in treatment resultsrnthe non viability (or death) of (oo)cysts. The physico-chemical parameters (temperature andrnfree chlorine residue) significantly correlated with the occurrence of (oo)cyst (p