Seinäjoki Adult Asthma Study is a single-centre 12-year follow-up study of a total cohort of 259 patients having new-onset asthma that was diagnosed at adult age. The study was divided in two parts: the collection of the original cohort (phase I;n=259) and follow-up visit (phase II; n=203). The aim of this study is to increase the understanding on the diagnostics and diagnostic process, organisation of the long-term asthma care, therapeutic outcomes, prognosis and the factors affecting the prognosis of new-onset asthma diagnosed at adult age.