In this article, we present a mathematical model to describe the diffusion of dextran through spherical microcapsules. Dextran was first allowed to diffuse into the microcapsules for a certain length of time (loading period). After the loading process was complete, the microcapsules were immersed in water medium, and the released concentration of dextran in the medium was measured over time. To demonstrate the applicability of the diffusion model, it was fit to the dextran release data (Gupta et al., 2004), and estimates of the diffusion coefficients in the core and wall of a microcapsule were obtained. From such estimates, one may be able to characterize the diffusion (or release) properties of microcapsules with different wall or membrane thicknesses, wall constitutions, loading times, and dextran molecular weights. Results from such a model can help in the planning and design of experiments.