Six generations of lactodendrimers based on poly(amidoamine) were studied in dilute solutions of 0.2 M NaCl by methods of molecular hydrodynamics (velocity sedimentation and viscometry) and optics (static and dynamic light scattering). Molecular weights, sedimentation and diffusion coefficients, and intrinsic viscosity values were measured. These data were analysed and compared with previous results for lactodendrimers. The values of hydrodynamics invariant and average substance density in a dendrimer molecule are discussed. The volume occupied by lactogroups was evaluated and it was shown that lactogroups do not experience strong steric hidrances in lactodendrimer molecules. (C) 2001 Elsevier Science Ltd. All rights reserved.