Production of monodisperse multivesiculated particles (MVPs) of polyester reticulated with styrene was studied using a T-junction device for droplet generation. The process is based on a w/o/w double emulsion, which after crosslinking and drying yields solid particles filled with closely packed microvoids. The effect of continuous and dispersed phase flow rates, protective colloid concentration, and temperature on droplet size was studied. SEM analysis of internal morphology of particles produced using a one-step double emulsification process indicated that vesiculation was sparse and mostly located in the particle outer layer. This was attributed to the long time needed for water diffusion to fill-in the organic droplets. Much better results were obtained using a two-step emulsification process, in which water was pre-emulsified in the organic phase, and the final double emulsion was generated in the T-junction. Monodisperse particles with uniform vesiculation throughout the entire core were obtained in this way. The pre-emulsion was observed to be more stable when using triethanolamine instead of diethylenetriamine as w/o stabilization promoter, allowing for continuous production for longer runs. (C) 2013 Elsevier B.V. All rights reserved.