Giardia infection is associated with diarrhea! diseases among infants and young children in both in dustrialized and developing countries. A study was conducted to demonstrate the predisposing factors for occurrence of the first symptomatic Giardia infection among infants in rural Egypt. The study cohort was followed from birth through the first year of life. Univariate and multivariate analyses of data revealed that infants less than six months of age were at special risk for developing their first symptomatic infection compared with infants more than six months of age. Analysis of the data, furthermore, revealed an increased risk of infant Giardia infection associated with living in a household without a latrine (relative risk [RR]= 2.63, confidence interval [CI]= 1.4-4.9, P< 0.05), a mud floor in the sleeping rooms (RR= 1.79, CI= 1. O30-3.0, P< 0.05), and household exposure to more than 10 chickens (RR= 2.5, CI= 1.13-5.56, P< 0.05). In contrast, the mother's education beyond the primary level