Nanoparticle formation using reverse micellar route has been applied to a large variety of nanoparticles in the recent past. In all these preparation methods, two micellar solutions containing reactants are brought together in small volume containers and the contents are agitated. While the mixing issues may not be important for such small-scale operations, large-scale production using this method will call for mixing of large volumes of micellar solutions in either batch systems or continuous reactors. The present study brings out the effect of inefficient mixing on large-scale operations by combining an approximate population balance model for particle formation proposed in this work with an existing model for mixing in turbulent flows. The approximate population balance model has been validated by comparing results with rigorous Monte-Carlo simulations for several cases. The model for capturing the effect of mixing on final particle size distribution visualizes competition between particle growth and formation of new nuclei to be similar to that known for series-parallel reactions. The present study predicts strong effect of intensity of mixing on both the average particle size and the breadth of the size distribution of nanoparticles, indicating that scale up of this process will require considerable care. (c) 2005 Elsevier Ltd. All rights reserved.