The Lung Tissue Research Consortium (LTRC) is a network of centers cooperating to harvest and process lung tissue specimens for use in scientific studies of the etiology and pathogenesis of lung diseases, especially chronic obstructive pulmonary disease (COPD) and idiopathic pulmonary fibrosis (IPF). In addition to carrying out tissue-based research in the participating Clinical Centers, the LTRC prepares collections of specimens, linked to clinical data describing the donor subjects, for widespread distribution to investigators for use in their research. The NHLBI authorizes distribution of available specimens and data collected by the LTRC to investigators, both within and external to this Consortium, based on evaluation of specific research proposals by a Protocol Review Committee.