Azapropazone loaded microspheres were prepared using bovine albumin as a controlling matrix. The cross- linking of bovine albumin was achieved using glutaraldehyde at three different concentrations. Drug incorporating eficiency of around 81% could be achieved through using this technique of preparation. In-vitro release of the drug was examined in simulated intestinal fluid, pH 7.4 at 37°C for microspheres having different glutaraldehyde concentrations, varying particle sizes and different drug loadings. It was observed that the release was diffusion controlled and followed the Higuchi model. Release characteristics were influenced by glutaraldehyde concentration, particle size and drug loading. The bioavailability of azapropazone released from the microspheres of different corss-linking concentrations was studied in rabbits following single oral administration. Microspheres with higher glutaraldehyde concentration was found to control azapropazone release even up to 12 hours. The peak serum concentration of such microspheres were well within the therapeutic level. The study demonstrated the potential of cross-linked bovine albumin as a matrix for controlled release oral preparations.2