Chitosan microspheres can be used in several applications, as biomaterials, in biotechnology processes and as adsorbents. The control of particle size in microsphere production is important to make these applications viable. This study focuses on the production and morphological characterization of chitosan microspheres. Microspheres were prepared by a spraying and coagulation process. Particles underwent chemical modifications with glutaraldehyde, epichlorohydrin or acetic anhydride treatments. The microspheres presented a fairly good sphericity (0.74) but an irregular micro-surface morphology. The mean particle size (MPS) ranged from 140 to 281 mum and the mean standard deviation (MSD) from 119 to 238 mm. The conditions were modelled to provide desired MPS and MSD by using the response surface methodology (RSM).347352Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)