Asthma is a complex disease that takes many different forms. There is some debate about whether asthma is really one disease or a set of different diseases that share some characteristics. By understanding the variation in how asthma presents, we hope to gain greater insight into how asthma might be caused. THis project will be part of a network of similar studies in both high and low income countries to see whether the factors that are associated with different asthma types vary by the sort of environment in which people live.