Office spirometry used to detect COPD in smokers ages 44 and above with respiratory symptoms probably meets the criteria for a population-based screening test and for clinical case finding: If not detected early, COPD causes substantial morbidity or mortality, and smoking cessation is more effective when COPD is recognized before exertional dyspnea develops. Office spirometry is a feasible testing strategy and may be used to encourage smoking cessation efforts that change behavior in at least some patients. Office spirometry is relatively simple and affordable, is safe, and includes an action plan with minimal adverse effects. On the other hand, the false-positive and false-negative rates of office spirometry in the primary care setting may be higher than diagnostic spirometry performed during epidemiologic studies or in diagnostic pulmonary function laboratories, and the incremental benefit of office spirometry on smoking cessation rates is poorly established (when added to referral to an AHCPR-based smoking cessation program).