Physical activity (PA) and exercise are interrelated but separate concepts. PA refers to bodily movement produced by skeletal muscles that results in energy expenditure. Exercise is a subset of PA, in which generally higher levels of muscular activity are performed for a purpose, such as achieving physical fitness or winning a sporting contest. Higher exercise capacity is considered to be permissive of greater PA in the home and community settings. Individuals with chronic obstructive pulmonary disease (COPD) are physically inactive when compared with healthy age-matched control subjects. Furthermore, physical inactivity is independently associated with adverse outcome in patients with COPD, including more rapid disease progression, impaired health status, and increased health care utilization and mortality risk. While there are several methods to objectively measure PA, recent scientific studies have commonly utilized questionnaires and activity monitors. The latter include simple pedometers and complex accelerometers, which can measure and record movement in up to 3 planes. In COPD, multiple patient characteristics and disease severity markers are related to activity level, including pulmonary physiological abnormalities such as airway obstruction and hyperinflation; exercise capacity such as the 6-minute walking distance; exacerbations of respiratory disease; and comorbid conditions. Clinical trials of bronchodilators, supplemental oxygen therapy, exercise training or pulmonary rehabilitation, or PA counseling have provided inconsistent results in demonstrating increased PA from the interaction. This is probably because the phenomenon of physical inactivity is complex, resulting not only from physiological impairments, but symptoms, cultural, motivational, and environmental factors.