Giardia lamblia exist in two forms one is cyst and other is trophozoite. it's Four pairs of flagella two nuclei and a sucking disk on the ventral surface with which it absorbs nutrient from intestine cause malabsorption by lashing movement of thread like flagella. Trophozoite is pear shape and 9.5 to 21um long and 5 to fifteen um in breadth . Trophozoite form like tiny water droplets when see dorsally and swollen sort of a bowl from side appearance. The pattern of nuclei, median bodies and axonemes match to a mammal countenance . Trophozoite appear in liquid and soft stool. it's infectious form after excystion start to multiply by adhereing to the wall of intestine . Cyst is oval shape and have a thick resistant wall around itself thanks to which it can survive for an extended period outside the body. Cyst was 12um long and 7-10 um in its width. Mature cyst has four nuclei curved median bodies and linear axonemes. It can survive in humidity and watery conditions. If a traditional chlorine concentration was used for the purification of water upto 3 months a minimum of . Cyst ingested cause excystation firstly in stomach and this go upto intestine and produce two trophozoites.