Abstract : Giardiasis is the most common protozoan parasites diagnosed in the pathology departments of health centers in the State of Bahrian. In 1982 a sample of 300 persons were parasitologically and serologically examined for intestinal parasites in Al Zin Area. There were 26 cases with Giardiasis, 23 of them were positive in counter immunoelectrophoresis test. In 1983 all records of stool parasitological examinations in Salmaniya Medical Centre were studied. Totally 9664 records 100 persons of the above records were serologically examined by CIT with 93% positive. The incidence of Giardia lamblia amongst the families of infected persons of the above sample was higher than the families of non-infected persons. The community based study of 0.06 of the population (2123 persons) of 1981 census shown 189 person (8-9%) with positive stool examination and 221 (10.4%) positive CIT whom 23 persons of them have been infected previously with Giardia, and 9 with negative stool examination. The study shows 100% sensitivity with high specific CIT. The epidemiological and parasitological examination of farmers, sewages and water samples of the agricultural areas revealed several intestinal parasites that explains the possible transmission through vegetables contamination rather than drinking water.