For many patients with advanced chronic airflow limitation (COPD) the treatment of dyspnea remains inadequate despite medications, rehabilitation programs, and supplemental oxygen. Bilateral carotid body resection (BCBR) is a controversial operation which has been reported anecdotally to relieve dyspnea in such patients, but its risks and long-term effects are not known. We studied pulmonary function and the ventilatory response to exercise of three severely dyspneic COPD patients who had chosen independently and without our knowledge to undergo this operation. All three patients reported improvement in dyspnea following BCBR despite the absence of improvement in their severe airflow limitation (mean FEV1 = 0.71 L before and 0.67 L after BCBR). The three patients died 6, 18 and 36 months after the removal of their carotid bodies, still convinced of the efficacy of their surgery. Their reported relief of dyspnea was associated with substantial decreases in minute ventilation and deterioration in arterial blood gases. Arterial blood gases worsened both at rest (PO2 fell from 57 to 45 mm Hg; PCO2 rose from 45 to 57 mm Hg) and during identical steady state exercise (at peak exercise, PO2 fell from 46 to 37 mm Hg and PCO2 rose from 50 to 61 mm Hg) postoperatively. Total minute ventilation decreased postoperatively both at rest (-3.4 L/min, -25 percent) and with exercise (-9.4 L/min, -39 percent) primarily because of decreases in respiratory rate (from 21 to 16 breaths/min at rest and from 25 to 18 breaths/min with exercise), and this was associated with decreases in both oxygen uptake (-26 percent) and carbon dioxide production (-22 percent) for the same external exercise workload. Whether the reported improvement in dyspnea was due to decrease in ventilation resulting from decrease in respiratory drive, a surgical placebo effect or some other unestablished effect of removal of the carotid bodies deserves further study.