COPD is a heterogeneous collection of conditions that can affect various structures within the lung in a number of different ways. These various processes can all result in limitation of expiratory airflow. If severe enough, this physiologic abnormality defines COPD. The various conditions that can lead to this syndrome are prevalent and often relentlessly progressive. In aggregate, they represent an important public health problem. This supplement outlines diagnostic and therapeutic strategies by which the practitioner can assist patients suffering from this condition.