A method for producing composite particles using a supercritical fluid extraction technique on an emulsion. First and second materials (for example; a polymer and a biologically active material) are dissolved or suspended in a preferably solvent to form a solution or dispersion. The solution or dispersion is emulsified in a polar solvent to form an oil-in-water or water-in-oil-in-water emulsion. The emulsion is contacted with a supercritical fluid to extract the solvent. Removal of the solvent by the supercritical fluid from the emulsion supersaturates at least the first material in the solution causing the first material to precipitate out of the solution as composite particles that include both the first and second materials.