Abstract: The invention relates to a process for improving the stability with respect to UV radiation of a photosensitive sunscreen agent, comprising the incorporation of said screening agent in a material prepared by the sol-gel route from at least one silicon alkoxide and from at least one surfactant. It is also targeted at a photostable material which comprises the combination of a photosensitive sunscreen agent and of a photostabilizing material prepared by the sol-gel route including at least one silicon alkoxide and at least one nonionic surfactant and at a cosmetic and/or dermatological composition comprising, in a cosmetically and/or dermatologically acceptable vehicle, an effective amount of a photostable material. This cosmetic and/or dermatological composition is intended mainly for protecting the skin and/or keratinous substances against ultraviolet radiation.