A new oscillatory device administers predetermined pressure oscillation sequences into the chest cavity over inhaled/exhaled air streams at low positive pressure. We assessed device safety and effect on 6MW performance, pulmonary function, and health-related quality-of-life (HRQOL) in moderate-to-very severe COPD in a randomized, double-blind, controlled, crossover study. Outcomes with an oscillatory device (Pulsehaler(TM), Respinova Ltd, Herzliya, Israel) and a "muted" sham device (control) of identical appearance that delivered continuous positive air pressure were compared in two groups receiving opposite treatment sequences: 2-week oscillatory device/control, 2-week washout, 2-week control/oscillatory device, 2-week washout. The clinical trial was registered ( www.clinicaltrials.gov , NCT00821418) and approved by the Hadassah-Hebrew University Medical Center Institutional Review Board (08-608). All participants signed informed consent; 22 patients completed the study with no marked differences in COPD exacerbations or side effects. A total of 91% of patients treated with the oscillatory device had a clinically significant improvement (increase >40 m) in 6MW performance. The 6MW distance with the oscillatory device increased significantly after 1 week of treatment (51.6 ± 7.6 m, +13.5 ± 2.3%, p < 0.001), and more after 2 weeks (61.8 ± 9.0 m, 16.3 ± 2.7%, p < 0.001). This increase with the oscillatory device was significantly greater (p < 0.001) than the 15.4 ± 10.4 m increase (4.2 ± 2.6%, NS) with control. FVC and inspiratory capacity (IC) improved significantly (p = 0.03 for each) with the oscillatory device but not with control. HRQL improved markedly (≥1 point) for dyspnea and mastery with the oscillatory device (p = 0.02) but not control. Treatment with a new oscillatory device appears to be safe, and to improve 6MW performance, pulmonary function, and HRQL in COPD. Further evaluation is warranted.