In this issue of CHEST (see page 1590), Weiss and colleagues24 report on the first, to our knowledge, randomized, placebo-controlled trial of MSCs (Prochymal; Osiris Therapeutics Inc) for therapy of moderate to severe COPD. The trial involved six centers and collected extensive baseline information and cardiopulmonary physiology on the 62 patients enrolled. MSC and placebo groups were well matched with the notable exceptions of more smokers in the placebo group and slightly older patients in the MSC group. MSCs (100×106) or vehicle were infused monthly for 4 months, and patients were followed for 2 years with measurements of pulmonary physiology, exercise capacity, subjective quality of life, and serum inflammatory markers. All patients underwent the planned four infusions, and none experienced infusion-related toxicities. Most adverse events were mild to moderate; although seven patients receiving MSC and five patients receiving placebo had severe adverse events (including three and two deaths, respectively), none of these events was deemed related to the study drug. There were no changes from baseline in echocardiographic findings, pulmonary function tests, 6-min walk distance with pulse oximetry, subjective measures of dyspnea, COPD exacerbations, or serum transforming growth factor-β or C-reactive protein (CRP). Post hoc analysis of patients with an elevated baseline CRP showed a mild decrease in CRP, but only at 1 month after the first MSC infusion.