This study examined the relationship between residence near major roads, traffic flow, and risk of hospital admission for asthma in children younger than 5 y of age living in Birmingham, United Kingdom. Area of residence and traffic flow patterns were compared for children admitted to the hospital for asthma, children admitted for nonrespiratory reasons, and a random sample of children from the community. Children admitted with an asthma diagnosis were significantly more likely to live in an area with high traffic flow (> 24,000 vehicles/24 h) located along the nearest segment of main road than were children admitted for nonrespiratory reasons (p < .02) or children from the community (p < .002). A significant linear trend was observed for traffic flow (p < .006) for children living less than 500 m from a main road but not for those living farther away. Children admitted for nonrespiratory reasons were more likely to be admitted than children in the community sample if they lived within 200 m of a main road (p < .02), irrespective of traffic flow.