Endothelin-1 (ET-1) is implicated directly in the progression of cardiovascular diseases (Luscher and Barton 2000), and a number of polymorphisms for ET-1 and endothelin receptor genes have been identified that are associated with increased risk for pulmonary and cardiovascular conditions (Charron et al. 1999; Dong et al. 2004; Immervoll et al. 2001; Jin et al. 2003). The gene discussed is EDN1; the disease is cardiovascular disorder.