Late diagnosis is the problem of chronic obstructive pulmonary disease (COPD). A patient with COPD, comes to see his doctor often when symptoms have occurred. By that time, lung function has already diminished by a third or one half. A single but good FEV1/FVC curve can detect the smoker who risks to develop an airway obstruction. The generalist can modify the patients' prognosis by performing this simple spirometry, encouraging smoking cessation and taking into account the patient's risks factors.