We investigated microcapsules composed of the weak polyelectrolytes poly(allylamine hydrochloride) (PAH) and poly(methacrylic acid) (PMA) assembled on calcium carbonate cores. These capsules are stable in the PH range from 2.5 to 11.5, undergoing reversible swelling in the PH interval from 2.7 to 2.6. Capsule swelling occurs at a protonation degree above 90%. The pH-dependent size variation of PAW PMA capsules is blocked after crosslinking of the polyelectrolyte layers.