A new method for the synthesis of protein microspheres of wide size range having good spherical geometry and hydrophilicity using very low concentrations of polymeric dispersing agents is reported. The method involves the use of around 1% solution of a biomedical grade aliphatic polyurethane in a mixture of a hexane and dichloromethane as the dispersion medium, as opposed to a 25-30% solution of polymeric dispersing agents employed by previous workers to effect steric stabilization of the protein solution droplets. The versatility of the method is demonstrated by the synthesis of albumin microspheres, as well as those of the amphiphilic protein casein, the latter being more difficult to prepare by surfactant stabilization techniques. Significant advantages of the method include the avoidance of surfactants which become adsorbed on the particles and influence tissue reactions and drug release, and the ease of removal of the polymeric stabilizer from the final product. The method may find application for the preparation of a wide range of protein and polysaccharide microspheres for medical use.