The ECLIPSE study characterized the heterogeneity of chronic obstructive pulmonary disease (COPD) in a large, well-characterized cohort of 2164 COPD patients, 337 smokers with normal lung function, and 245 never-smokers. COPD patients were older and had higher smoking exposure than smokers with normal lung function. They also had more co-morbidities, which were not related to GOLD stage. The severity of airflow limitation was poorly correlated with symptoms, health status, and exacerbations. Emphysema increased with GOLD stage, and bronchiectasis was low but also increased with stage. Gender differences were observed, with females having less smoking exposure and more exacerbations. The study found that the GOLD classification based on airflow limitation was a poor predictor of other disease features. The BODE index, a multidimensional grading system, showed similar results. The study highlights the complexity of COPD and the need for a more comprehensive approach to its management, beyond spirometry alone. The findings suggest that COPD is highly heterogeneous, and the current GOLD classification may not fully capture this diversity. The study also identified potential gender differences in COPD, with females being more susceptible to certain co-morbidities. The results emphasize the importance of considering clinical, functional, and radiological variables in assessing COPD severity. The study was sponsored by GlaxoSmithKline and involved multiple centers across 12 countries. The findings have implications for the future management and understanding of COPD.The ECLIPSE study characterized the heterogeneity of chronic obstructive pulmonary disease (COPD) in a large, well-characterized cohort of 2164 COPD patients, 337 smokers with normal lung function, and 245 never-smokers. COPD patients were older and had higher smoking exposure than smokers with normal lung function. They also had more co-morbidities, which were not related to GOLD stage. The severity of airflow limitation was poorly correlated with symptoms, health status, and exacerbations. Emphysema increased with GOLD stage, and bronchiectasis was low but also increased with stage. Gender differences were observed, with females having less smoking exposure and more exacerbations. The study found that the GOLD classification based on airflow limitation was a poor predictor of other disease features. The BODE index, a multidimensional grading system, showed similar results. The study highlights the complexity of COPD and the need for a more comprehensive approach to its management, beyond spirometry alone. The findings suggest that COPD is highly heterogeneous, and the current GOLD classification may not fully capture this diversity. The study also identified potential gender differences in COPD, with females being more susceptible to certain co-morbidities. The results emphasize the importance of considering clinical, functional, and radiological variables in assessing COPD severity. The study was sponsored by GlaxoSmithKline and involved multiple centers across 12 countries. The findings have implications for the future management and understanding of COPD.