COPD is characterized by airflow limitation. The diagnosis is suggested by history and physical examination and is confirmed by spirometry (ie, a low FEV(1) level that is unresponsive to bronchodilators). Once diagnosed, there is no widely accepted staging or severity scoring system. COPD presently is graded using a single measurement such as FEV(1), which, unlike the case with asthma, has a limited role in disease management. A more comprehensive staging system is required incorporating, for example, age, arterial blood gases, dyspnea, body mass index, and distance walked, in addition to FEV(1). These criteria should allow for more evidence-based recommendations for management of this condition. Asthma is an inflammatory disease also characterized by airflow limitation. But in contrast with COPD, the airflow limitation is highly reversible either spontaneously or with therapy. Repeated lung function measurements using portable peak flowmeters have resulted in improved outcomes. Therefore, frequent flow determination is recommended in the routine management of asthma. Treatment with anti-inflammatory agents and close monitoring of lung function should help decrease the morbidity and mortality associated with asthma.