The size and molecular mass of water-soluble interpolyelectrolyte complex (PEC) formed between poly(L-glutamate) and poly(amido an-tine) dendrimer in aqueous solution were estimated as a function of the decreasing pH from the turbidities (tau) and their wavelength dependence, by comparison with numerical tau calculations by applying the Rayleigh-Debye-Gans and Mie scattering theories. Close to the pK(a) of the peripheral amino groups of the dendrimer, PECs with densities comparable to that of fractal clusters from a reaction limited colloid aggregation process collapsed to dense particles with similar to1 mum diameter. At a pH close to the pK(a) of the amino groups in the interior of the dendrimer, systems with carboxylate excess over amino/ammonium groups formed compact particles, and ion pairing likely extended to the ammonium groups in the dendrimer interior. PECs with the highest polymer density were formed at the stoichiometric ratio: They appeared to be stable against dissociation at pH 3 in contrast to PECs formed with high dendrimer excess.