1.1 Description of the study population Children will be recruited from Nandipara, a peri-urban community situated 7 miles northeast of Dhaka City. This community has a population of 3,500 in an area of approximately 2.5 square miles. Among the residents, 70% of males are classified as day laborers, 20% are rickshaw pullers, and 5% are carpenters or service holders. Fifteen percent of women are day laborers and 85% are housewives. The average family size is 4.5 members. The slum has a municipal water supply for drinking and cooking and most families live in poorly constructed houses. The great majority of houses are mud walled with thatched dry leaves and bamboo or tin roofs. The population less than five years of age is about 700. The prevelance of H. pylori infection in less than five children in this community is 50%.44 A weekly clinic has been run by the International Centre for Diarrhoeal Diseases Research, Bangladesh (ICDDR,B) for minor case of illness in the population since 1986.