We determined the prevalence and risk factors of H. pylori infection among 197 healthy 3- to 5-year-old Israeli Arab children, in a population under socioeconomic and environmental transition. Data on the socioeconomic and environmental characteristics were obtained by personal interviews. The presence of H. pylori infection was identified using an ELISA kit for detection of H. pylori antigens in stool specimens. The prevalence rate of H. pylori infection was 49·7% (95% CI 42·8-56·67). It varied significantly among the different villages. In the univariate analysis stratified by village, the risk of infection increased according to household crowding, number of siblings younger than 5 years and siblings' H. pylori positivity. In the multivariate analysis the village of residence and siblings' 'H. pylori' positivity were the only variables that remained strongly associated with 'H. pylori' infection. In a population such as that described in this study the socioeconomic and living conditions are major risk factors of 'H. pylori' infection and the intra-familial transmission of 'H. pylori' in early childhood has an important role.