The study applied statistical linkage analysis to family data. Pulmonary measurements had already been collected on 159 members of 16 pedigrees and evidence supporting a COPD susceptibility gene in these pedigrees had been obtained from segregation analysis. Each of 11,995 genetic markers, which had already been genotyped on pedigree members, were tested for evidence of linkage to the inferred COPD susceptibility gene. Evidence of linkage to one or more genetic markers identifed genomic locations of COPD susceptibility genes. The high density of markers allowed fine-mapping of the gene. Successful completion of this gene localization project was the necessary prerequisite for a project to identify and characterize a COPD susceptibility gene. Identifying a gene that when mutated increased the risk of COPD may increase understanding of pulmonary function, as well as allowing gene-carriers to be identified and made aware of their susceptibility.