The sequential development of allergic disease manifestations during early childhood is often referred to as the atopic march. Various epidemiologic and birth-cohort studies have begun to elucidate the evolution of allergic disease manifestations and to identify populations at risk for disease. These studies, along with intervention studies, emphasize the effects of environmental factors and genetic predisposition on the atopic march. This article discusses the populations at risk for the development of atopic conditions and the interventions that have been explored in attempts to modify the progression of allergic disease.