We will also perform a prospective longitudinal study on IPF patients and their household partners. IPF subjects are included if they have no other pulmonary disease and the diagnosis of IPF is confirmed by lung biopsy or by clinical and chest CT findings. The control group will consist of subjects without respiratory symptoms or pulmonary diseases who are the household partner or spouse of an enrolled IPF subject and who accompanies the IPF patient to outpatient clinic visits. If there is no household partner, or if the partner is unwilling to participate, we will still enroll the IPF subject who qualifies for the study and is willing to participate. Saliva, induced sputum, and venous blood will be collected from IPF and control subjects after informed consent at each clinic visit. Visits usually are at approximately 3-4 month intervals over a one year period.