Submicron organic particles are produced by precipitation in an emulsion. The poorly water soluble organic substance is dissolved in a non-polar solvent. This solution is dispersed in an aqueous phase in the presence of emulsifier. When the non-polar solvent is removed by evaporation, the organic substance precipitates and one particle is formed in each emulsion droplet. Experimental work are here reported on the rate and the influence of the evaporation rate on the formation of cholesteryl acetate particles. An introductory theoretical analysis of the conditions experienced by each droplet during the evaporation is given. The experimental results suggest that the evaporation of the solvent is a rapid process mainly determined by the transport of the droplets to the vicinity of the air water interface. However, the results also show that the size of the particles formed by precipitation in the emulsion, is insensitive to the evaporation conditions, for instance if the evaporation is artificially slow. The particle size is mainly governed by the size of the emulsion droplets. The analysis discuss the possibility that during the evaporation of the emulsion, each individual droplet is emptied of its content of the non-polar solvent very rapidly. The hypothesis that each solid particle is formed during a very short period of time without obtaining a concentration equilibrium within the droplet is tested. However, the order-of-magnitude estimations do not support a kinetic explanation for the fact that the particles obtain the size of the emulsion droplets.