Sedimentation velocity runs were performed on organic and inorganic particles with analytical ultracentrifugation and the diameter and diameter distribution analysis was carried out with Sedfit and VelXLAI data analysis programs. The particles were measured either as pure components or as mixtures of different organic or inorganic particles using different weight ratios of these components. Polymer particles with peak diameters of approximate to 15 and 32-35 nm and inorganic particles with peak diameters of approximate to 5 and nm were used and the particles also differed in the extent of polydispersity. The mixtures of particles in the weight ratios of 50:50, 90:10 and 95:5 of smaller to larger particles or vice versa were studied. The aim was to compare the performance of the analysis programs to characterize the various polymer and inorganic particle samples of varying complexity. The analysis programs were compared with each other not only for peak particle diameters and their size distributions, but also for the cumulative fractions of components of the particle mixtures. (C) 2010 Elsevier Inc. All rights reserved.