In this study microspheres of diclofenac sodium, an anti-inflammatory agent, were prepared by utilizing a natural polysaccharide, chitosan-H. The objective of this investigation was to sustain the action of diclofenac sodium and to show the effect of various conditions on release kinetics. For this reason factorial design experiments were performed. The independent variables in the 3(3) factorial design were chitosan-H concentration, tripolyphosphate concentration and stabilization time, and in the 3(2) factorial design were chitosan-H and tripolyphosphate concentrations. The dependent variables, t(50%) and the total drug content were investigated by the polynomial equations. The release profiles were evaluated kinetically and the best fit was obtained by the Higuchi equation.