Continuous powder mixing is an efficient alternative in high volume manufacturing of powder-based products. A new method is communicated in this paper to determine the effects of different operating conditions and mixer configurations on mixing performance. The main idea of the proposed methodology is the utilization of experimental residence time distribution (RTD) measurements to (a) determine the contributions of feeding variability, powder segregation and RTD variability on output composition variance and (b) develop a predictive model of the output variance of a continuous mixer. The method is illustrated using experimental data for mixing acetaminophen and lactose in convective continuous mixer. (C) 2010 Elsevier Ltd. All rights reserved.