Hollow spheres of aromatic polyamide are obtained by the reaction-induced phase separation during polymerization of 5-hydroxyisophthalic acid and 1,4-phenylene diamine in an aromatic solvent at a concentration of 1-2% at 320 degrees C without stirring. The hollow sphere has a dimple hole and the diameters of the hollow spheres are 3-4 mu m. The droplets are initially generated via liquid-liquid phase separation and then rigid crosslinked network structure formed the rigid skin layer on the surface of the droplets. The solidification of the droplets occurred owing to the further polymerization in them with maintaining the morphology to form the hollow spheres. The hollow spheres exhibit outstanding thermal stability. (C) 2012 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 780-785