The membrane emulsification method was adopted to prepare monodisperse albumin microspheres. Uniform-sized emulsion droplets were successfully obtained by passing albumin solution through the membrane into kerosene at appropriate applied pressures. After heating the emulsion, monodisperse albumin microspheres were prepared and the heat-denaturing process itself did not affect their monodispersity once uniform emulsion droplets had been prepared. The shape and size of the albumin microspheres were strongly dependent on the concentration of the albumin solution and the heat denaturing temperature. Lower albumin concentrations produced non-spherical particles and higher denaturing temperatures made the particles smaller. Incorporated riboflavin released quite rapidly from the albumin microspheres, and increases in both albumin concentration and denaturing temperature caused the drug release to be sustained, presumably because a rigid and dense matrix was formed within the albumin microspheres.