Particle masses of the order of 10(8)-10(10) g mol-1 and the radii of gyration and hydrodynamic radii of spherical poly(methyl methacrylate) particles were characterized by combined static and dynamic light scattering. The dispersions were prepared by dispersion polymerization and stabilized by polystyrene-block-poly(ethylene-co-propylene). The radii of gyration were calculated from the measured particle scattering intensity by fitting procedures using the Rayleigh formula for spheres. This practice allows the use of all points actually measured instead of the uncertain values at low angles only. The strongly disturbing influence of small contents of large particles (aggregated particles, dust) was eliminated. The autocorrelation functions were measured by dynamic light scattering and analysed by the Contin procedure. The coronas and densities of the particles could be characterized on the basis of the geometric radii of the pure main components.