The underlying pathogenesis of asthma, one of the most common chronic diseases of childhood, is not fully understood. There is a well-documented heritable component to this disease and environmental factors associated with a Westernised lifestyle have also been implicated; recent studies suggest gene-environment interactions are important in the development of this disease. In the absence of a previous review in children, the present report presents the accumulating evidence for gene-environment interactions in asthma pathogenesis. Studies of these interactions in different populations have yielded both expected and unexpected results. This is a new and rapidly developing field where there are currently many more questions than answers.