Financial/nonfinancial disclosures: The authors have reported to CHEST the following conflicts of interest: Dr Busse has provided consultancy/advisory board services to Alexon, AstraZeneca, Altair, Amgen, Abbot Laboratories, Asthmatx, Inc, Boehringer-Ingelheim, Bristol-Meyer Squibb Company, Centocor, Dainippon Sumitomo, Funxional Therapeutics, Ltd, GlaxoSmithKline, Pfizer, Genentech, Johnson & Johnson, Merck, Novartis, Schering-Plough, TEVA, and Wyeth; received lecture fees from Merck; received industry-sponsored grants from Novartis, MedImmune, AstraZeneca, Ception, and GlaxoSmithKline; and received National Institutes of Health (NIH) grant support from NIH-NIAID and NIH-NHLBI. Dr Chung has received grant funding from GlaxoSmithKline, MRC (UK), and Wellcome Trust, and has been renumerated for participation at advisory board meetings of GlaxoSmithKline, Merck, and Gilead. Dr Jarjour has received pharmaceutical company grant money from GlaxoSmithKline and Merck and has been a consultant to GlaxoSmithKline, Genentech, and Asthmatx. Dr Hunt is a shareholder in Respiratory Research, Inc and in Airbase Pharmaceuticals and is cofounder of Respiratory Research, Inc, which manufactures EBC collection equipment and has financial interest in EBC pH testing. He is an inventor of EBC pH assays, and his university owns IP on EBC pH testing. He speaks regarding EBC pH testing (no honorarium). He advises for Pulse Health, Inc, a company that studies exhaled breath for oxidant stress. He has received grant money from NIH and the UVA Philip Morris Tobacco Research Fund, and Respiratory Research, Inc. He is the founder of AirBase Therapeutics, LLC. Dr Gaston is a shareholder in Respiratory Research, Inc and in Airbase Pharmaceuticals. The remaining authors have reported to CHEST that no potential conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.