The pharmaceutical industry is in the midst of a major transition in manufacturing, which is focused on continuous operation. One of the transitioning operations is powder mixing, arguably the principal process in the product preparation. This work examined the performance of a new continuous tumble mixer. The study focused on the mixing capabilities and powder flow phenomena inside the mixer as a function of the inlet flow rate, mixer rotation speed, and material properties. The continuous tumble mixer achieved good mixing levels when consider the obtained relative standard deviation (< 5% in most cases) of the outlet concentration. A map of the material compressibility index was developed to relate the effect of the material properties and operating conditions to the powder behavior inside the mixer. The rolling, cascading, and, principally, cataracting regimes were obtained, which ensured blend uniformity. (C) 2014 Elsevier B.V. All rights reserved.