Method to increase the stability of nanocapsules during storage thereof

A method to increase the stability of nanocapsules during storage thereof wherein the nanocapsules are smaller than 0.5 micron and are formed with a lipid nucleus of a natural or synthetic origin and contain at least one chemically or biologically active substance surrounded by a polymeric wall of a synthetic or natural origin;

• comprising adding a cryoprotective agent in an aqueous dispersion of the nanocapsules while stirring until the monosaccharide cryoprotective agent in a concentration between 2 and 10% dissolves, subjecting the dispersion thus obtained to a temperature no lower than -40.degree. C. for about 2 to 4 hours, and eliminating water by heating progressively to a temperature of about 35.degree. C. at a reduced pressure, thereby providing a stable lyophilized product in the form of a fine powder.