Uniform polyurethaneurea (PUU) spheres were prepared from 20-40 wt % urethane prepolymer (UP) solution of xylene. Uniform droplets were formed with the Shirasu porous glass (SPG) membranes of 1.42, 5.25, and 9.5 mu m pore size, dispersed in an aqueous phase with dissolved stabilizers, and allowed to stand for the chain extension at the room temperature with diamines that were added after the emulsification. The reaction progressed rapidly by an addition of ethyl acetate to the aqueous phase, promoting the diffusion of diamines into the droplets. The reaction of -NCO groups with water did not hamper the emulsification process, which normally occurred in 1 to 2 h, yielding stable droplets with the coefficient of variation around 10%. No instability or coagulation occurred, while standing for the chain extension, and solid, spherical PW particles of 5-20 mu m were obtained after removal of the solvent.