A dispersion containing minute polymer beads possessing a thermosensitive characteristic is produced by a method which comprises preparing an aqueous solution of an acrylamide type vinyl compound, the homopolymer of which exhibits a hydrophilicity-hydrophobicity thermoreversible solubility characteristic, adding a cationic or anionic surfactant in a ratio equaling or exceeding the micelle concentration to the aqueous solution, adjusting the resultant aqueous solution to a temperature not lower than the clouding point thereof and, at the same time, polymerizing the acrylamide type vinyl compound in the aqueous solution thereby forming a polymer emulsion, exposing the emulsion to an ionizing radiation thereby cross-linking minute polymer beads in the emulsion, and thereafter depriving the resultant polymer emulsion of the surfactant.