Photoprotective cosmetic/dermatological compositions well suited for the UV-photoprotection of human skin and/or hair, comprise (a) particulates of at least one insoluble mineral and/or organic UV-screening agent having a particle size ranging from 5 nm to 5 m and (b) a stabilizing amount of at least one amphiphilic polymerizate of at least one ethylenically unsaturated monomer which comprises a sulfonic group, whether in the free acid or in partially or totally neutralized state, and which amphiphilic polymerizate also comprises at least one hydrophobic moiety.