Nano/micro sized particles of PMMA have been prepared by cooling in 1-propanol. Average particle size of 0.1-10 micron could be controlled by adjusting the cooling rate of 0.1-10 K/min and polymer concentration of 0.5-5 wt.%. Uniform spherical particles were obtained at the operating condition investigated. Particle size depends mainly on the cooling rate rather than on the concentration of the polymer solution. The average particle size is roughly the cubic root of the polymer concentration at a constant cooling rate. Linear cooling mode is recommendable for narrower particle size than natural cooling mode. The higher metastable zone width leads to the larger particle size. By observing the dependence of the particle size on cooling rate, it was found that primary nucleation took place in the formation of polymer in solution. (c) 2005 Elsevier B.V. All rights reserved.