The present invention concerns microcapsules comprising a capsule core, a capsule wall and also, disposed on the outer surface of the capsule wall, a polyelectrolyte having an average molecular weight in the range from 500 g/mol to 10 million g/mol, the capsule wall being constructed from 10% to 100% by weight of one or more C.sub.1-C.sub.24-alkyl esters of acrylic and/or methacrylic acid (monomers I), 0% to 80% by weight of a water-insoluble or sparingly soluble in water bi- or polyfunctional monomer (monomers II), and 0% to 90% by weight of other monomers (monomer III) all based on the total weight of the monomers, wherein the microcapsules have an average particle size of 1.5-2.5 .mu.m and 90% of the particles have a particle size .ltoreq.4 .mu.m, a process for their production, their use in textiles, bindered building materials and heat transfer fluids, and also microcapsules as an intermediate product.