Hollow chitosan microspheres with and without genipin-cross-linking were prepared by an oil(1)-in-water-in-oil(2) emulsion solvent diffusion method without any surfactants and core templates. Aqueous chitosan solution and ethyl acetate were used as the water and oil phases, respectively. The effects of oil(1)/water ratio, oil(2) volume, cross-linker ratio and cross-linking time on the characteristics of the chitosan microspheres were determined. Chitosan microspheres with spherical shape and hollow structure were obtained. The density of the chitosan microspheres decreased slightly as the oil(1) ratio increased. The average particle size increased slightly as the oil(2) volume decreased and the oil(1) ratio, cross-linker ratio and cross-linking time increased. (C) 2013 Elsevier B.V. All rights reserved.