Chronic obstructive pulmonary disease (COPD) is the third leading cause of death in the United States and the only leading cause of death that is steadily increasing in frequency. This project collected a set of extended pedigrees ascertained through subjects with severe, early-onset COPD. This study has enrolled subjects with severe COPD (forced expiratory volume in one second (FEV1) < 40% predicted) at an early age (< 53 years) without alpha-1 antitrypsin deficiency (a known Mendelian risk factor for COPD). Extended pedigrees are enrolled, primarily in New England, although some more geographically distant subjects have been included. This study has been used for epidemiological studies, familial aggregation analysis, linkage analysis, and candidate gene association analysis. Approximately 80 of the severe, early-onset COPD probands will undergo whole genome sequencing in this project with sequencing data available through dbGaP.