The aim of this work was to select and characterize model particles, which correspond to real wear products from artificial hip joints, and to investigate the dispersing behavior of these powders. Commercially available nano and microparticles of corundum, graphite, and chromium oxide were selected or alternatively self-produced by milling. These powders were characterized regarding density, specific surface area, crystalline phases, particle size distributions and shape. Volume-based particle size distributions Q(3)(d) were measured after dispersing in water, water with dispersant, Ringers solution, and cell culture solution (Dulbecco's Modified Eagle's Medium (DMEM)) by laser diffraction and ultrasonic spectroscopy. Nanopowders formed agglomerates in the micrometer range in cell culture solutions. The micropowders showed only a marginal agglomeration. The median diameters of the dispersed nanopowders were even bigger than those of micropowders. Calculations of the number-based size distribution Q(0)(d) showed that in spite of the agglomeration the predominant number of the nano and microparticles is in the sub micrometer range, with only one exception, the micrographite powder.