Original natural trio] (castor oil) was used as a monomer for the synthesis of monodisperse polyurethane nanoparticles (size ranging from 200 to 400 nm) by miniemulsion technique in water. Various parameters such as the concentration of the reactants, the nature of stabilizers and the shear were tuned to control the particle size and its distribution. The polyaddition between the natural triol and isophorone diisocyanate (IPDI) was conducted at 60 degrees C, in the absence of catalyst and monitored by infrared spectroscopy. The characterization of these polyurethane latexes was carried out using light scattering measurements and transmission electron microscopy (TEM). (c) 2006 Elsevier Ltd. All rights reserved.