The use of biomaterials as drug delivery systems (DDS) eliminates the adverse side effects of systemic drug administration. Silica-based bioceramics have been widely studied as DDS and demonstrated a unique ability for controlled drug release locally that target infected bone tissues. Successful treatment using a DDS requires the release of a therapeutic dose of the drug for a period of time long enough to eradicate the infection. Porosity characteristics and chemistry of the scaffold can significantly control drug binding and release kinetics. In particular, many studies have demonstrated that the porosity percent and pore size distribution dictate the surface area of the material available for drug adsorption and the subsequent release inside the body. The two primary mechanisms governing the drug release from porous, inert bio-ceramic materials are the dissolution of the drug from the outermost surface and diffusion from the inner pores to the physiological solution. The former mechanism leads to a burst release phase while the latter leads to a sustained release phase. The present study uses a combination of experimental and theoretical approaches to study the relative importance of these two mechanisms and the influence of various porosity parameters on them.\parIn the experimental part of the study, porous alpha-Cristobalite ceramic discs were prepared using powder metallurgy techniques. The porosity characteristics of the ceramic discs were varied and characterized by mercury porosimetry. The discs (n = 4) were immersed in antibiotic solution (Vancomycin) for either 4 hrs or 24 hrs. The amount of drug adsorbed on the porous ceramic was determined and correlated to the porosity characteristics of the material. Moreover, the vancomycin release kinetics from porous alpha-Cristobalite samples into physiological solution was measured and correlated to the porosity characteristics and the initial drug adsorption. Concurrently, Fickian diffusion laws were used to develop the drug desorption and diffusion models from the alpha-Cristobalite disks. The governing differential equations for drug concentration were solved using the finite element software package ABAQUS. The computational results and the experimental data were used to determine the mass transfer coefficient and diffusion coefficient values for different porosities and drug immersion times. The role of drug desorption and diffusion mechanisms in drug release from porous alpha-Cristobalite was studied. The experimental results show that a higher percent of drug release was achieved for the disks with the highest porosity contributed by micro-size pores. The contribution of nano pores to the total surface area have resulted in lower rates of drug release during diffusion dependent sustained release stage. Lower values of diffusion coefficient indicate that the diffusion of drug through the porous ceramic matrix is very slow and that initial burst release is predominantly due to the dissolution process.