Aims : Asthma and COPD have long been considered to be distinct entities. However, in the past decade, we have come to realise that there are many patients with features of both. In this session, the science underlying airway obstruction, both reversible and irreversible, will be examined. Thereafter, we will give individual talks on the two major phenotypes in the syndrome, namely, asthma with features of COPD and COPD with features of asthma.