Powder mixing is an important operation routinely used in many industries, including pharmaceuticals. The quality of products depends on certain operating conditions, such as the equipment, technical parameters and formulation. In this work, an operational qualification of powder mixing during large scale production in a pharmaceutical industry was performed. A simple and practical protocol was followed. Using a V-blender and dry powder mixing, the operation was tested to illustrate the effect of mixing time on the homogeneity of the drug in the mixture, demonstrating that this parameter can be used as a secure parameter to control this pharmaceutical operation on a large scale during batch production and using an off-line monitoring technique. (C) 2009 Elsevier B.V. All rights reserved.