Ethylcellulose (the organic substance), ethanol (the solvent) and water (the nonsolvent) are chosen as a model system for the production of uniform nanoparticles by drowning-out. Experiments carried out under various operating conditions show that many process parameters, such as the type of stirrer and the stirring speed, the temperature and the solvent-nonsolvent ratio, have practically no influence on the formation of ethylcellulose particles. On the other hand, the ethylcellulose concentration in the initial alcoholic solution seems to be the most important parameter controlling the particle size distribution. A comparison is made between experimental results and predictions of classical nucleation theories or aggregative growth models.