Because polyelectrolyte complex formation is known to depend on charge densities of polyelectrolytes, influence of pH condition in the preparation of the polyelectrolyte complex capsules on their permeability characteristic for phenylethylene glycol was examined. Partly crosslinked polyelectrolyte complex capsules were prepared by addition of an aqueous poly(acry1ic acid) solution into an aqueous poly(ethy1enimine) or L-histidine-attached poly(ethy1enimine) (ethylenimine unit/L-histidine residue: 5/1, mol/mol) solution and subsequent crosslinking under various pH conditions. Although poly(acry1ic acid) and poly(ethy1enimine) change their charge density depending on pH in an aqueous solution, the resultant capsules prepared at pHs 7,6, and 5 show similar permeation properties under neutral and acidic conditions. By contrast, when L-histidine-attached poly(ethy1enimine) was used instead of the unmodified polymer as the capsule membrane component, the resultant capsules prepared a t pHs 8, 7, and 6 revealed remarkable difference in the permeability under neutral and acidic conditions. Because the ionization of a n imidazolyl group, whose pKa is 6, on the L-histidine-attached poly(ethy1enimine) is influenced significantly by pH near its pKa, such situation might affect density of networks formed by the ionic bonds in the polyelectrolyte complex membrane and resulted in the permeability difference.