Phase A: This phase will be a prospective cohort study of randomly chosen residents of two census subdivisions of BC with a self-reported physician diagnosis of asthma. The study participants will be recruited via landline and cell phone-based random digit dialing across two regions in British Columbia: the Census Sub-Division of the city of Vancouver and the Census Division of Central Okanagan. The target area was chosen based on Census Sub-Division as it provides a clear definition of the target population for whom demographic and socioeconomic data is available through national and provincial census and surveys. The Okanagan Census Sub-Division was particularly chosen as it provides data on both urban and rural populations (18.6% rural population in 2006). According to 2006 census profile, the population of these two Census Sub-Divisions is, respectively, 578,041 and 162,276. Accordingly, about 78% of participants would be recruited from Vancouver, and 22% from Okanagan. The study will randomly sample participants from all the area codes in these regions. The target population will include household residents residing in telephone exchanges within the target Census Sub-Divisions. Random digit dialing will be geographically stratified with an associated sample weight that will approximate a probability sample of the individuals in the population. Previous studies have shown that acceptably high response rates can be achieved among Canadian participants with asthma.