Background: Current DPIs on the market have fine particle fractions (FPF) in the range of 10-70%, produce high mouth-throat (MT) depositional losses of approximately 30-95%, and have relatively low and variable lung delivery efficiencies. A high efficiency dry powder inhaler (DPI) was developed and tested for use with carrier-free formulations across a range of different in vitro inhalation flow rates. Methods: The performance of the new design was investigated and reported in terms of aerosolization characteristics. The new design oriented the capsule chamber (CC) at an angle of 90 degrees to the main flow passage, which contained a 3D rod array for aerosol deaggregation. Results: Orienting the CC at 90o to the mouthpiece produced an albuterol sulfate emitted dose (ED) of 73.4%, fine particle fractions (FPFs) less than 5μm and 1μm of 95.1% and 31.4%, respectively, and a MMAD of 1.5μm when tested at a flow rate of 45LPM. The variability associated with both ED and deaggregation was low with the CC90-3D design when tested between 31.8 to 55.1 LPM, respectively. There was no significant change in emitted dose across the range of flow rates. FPF changes of approximately 1% in value and MMAD changes of approximately 0.1 μm in value, were observed. Conclusions: The new inhaler produced an extremely high quality aerosol with little sensitivity to flow rate and is expected to deliver approximately 95% of the ED to the lungs.