Chronic Obstructive Pulmonary Disease (COPD) is a leading cause of morbidity and mortality throughout a large part of the western world. Although personal tobacco use has been implicated in a large number of these cases, it is also true that only a fraction of smokers ever develop respiratory problems. Therefore, the question of host susceptibility and other environmental factors should be considered. This paper will briefly review evidence for host susceptibility to COPD, review evidence for additional environmental risk factors for the development of COPD, and give an example of environmental interactions with a known genetic risk factor that further increase the risk of COPD.