Acetylated and succinoylated inulin were synthesized by reacting inulin with acetic anhydride and succinic anhydride. The modified inulin was characterized by FTIR, NMR, and potentiometric titration. The compositional dependence of their properties, such as solubility, pKa, and melting point, was investigated. The results reveal that the solubility of the inulin derivatives in pH 7.4 buffer solution increases with the succinyl content, varying from negligible for fully acetylated inulin to over 54% for fully succinoylated inulin, whereas the corresponding pKa of the inulin derivatives decreases with increasing succinyl content. In addition, the melting point is lowered by acetylation and/or succinoylation. The influence of pH and ionic strength on the solubility of inulin acetate succinate was also studied. The solubility increases dramatically as the pH value approaches that of the pKa. Interestingly, in pH 7.4 buffer solutions of varying ionic strength, a maximum solubility appears at an ionic strength of 0.15M. This is interpreted as a result of a balance of the ion exchange process and the double layer suppression. Microspheres of inulin acetate and inulin acetate succinate with and without drug were prepared by the solvent precipitation method. Cationic compounds, chlorhexidine and chymotripsin, were used as model drugs. The size and morphology of microspheres were determined by scanning electron microscope. The microspheres range in diameters from 0.5 to 4 mu m for inulin acetate and inulin/chymotripsin microspheres, and from 90 to 130 mu m for inulin acetate/chlorhexidine microspheres. The cross-section of the microspheres exhibits a porous interior. Preliminary results show that the microspheres are able to release the incorporated drugs for an extended period of time.