A novel technique is described for preparing multiple polymeric microspheres of the same size. A monodisperse droplet suspension of an acrylic monomer was prepared in a T-shaped microchannel, and particles of accurately the same size were produced by subsequent polymerization. The droplet/particle size was varied flexibly in the range of diameters 30-120 mum by changing the flow conditions in a microfluidic device. The resulting products have a coefficient of variation (CV) below 2%. A diagram of the flow parameters showed a clear region in which monosized drops were formed successfully. Furthermore, using another microfluidic device, hemi spherically colored acrylic microspheres of 90-190 mum in diameter were engineered with a coefficient of variation of less than 1%. (C) 2003 Elsevier B.V. All rights reserved.