Introduction : Chronic obstructive pulmonary disease is a chronic inflammatory disease of the airways defined by bronchial obstruction that is not or only slightly reversible and characterized by a progressive decline in FEV1. Methods . In order to evaluate the progressive decline in FEV and identify predictive factors, we carried out a prospective epidemiological and longitudinal study spread over 3 years, including COPD patients.The latter benefited in a stable state from spirometry per year. Results : The average age of patients is 61 ± 9 years with a clear male predominance . The cumulative quantity of tobacco is 50 P/ A.The majority of COPD is of moderate stage 64.4 %. During the 36 months of follow-up, the average annual decline in FEV was 39.7 ± 23 ml . Smokers declined more than ex-smokers, 51 ml vs. 29 ml ( p : 0.000).There was a significant difference between the annual decrease in FEV1 and the GOLD stages; between stage II and III (44 mL vs 34 mL, T : 3.4, p < 0.05) and between III and IV (34 mL vs 22 mL T: −4.29, p < 0.05).The decline in FEV1 in frequent exacerbators is greater than that in less frequent exacerbators (44 ml vs 34,T:-2.61 Conclusion : Persistence of smoking and frequency of exacerbations are the main predictive factors of FEV1 decline in COPD subjects.