Inertial deposition of aerosol particles on single spheres and regular assemblies of spheres was investigated in the range of Stokes numbers from 0.03 to 5. Measurements were carried out on steel spheres suspended from wires in a 100 mm wide flow channel at air velocities from 5 to 28 ms(-1), using monodisperse DES (Di-II-ethyl-hexyl-sebacate) test aerosol in the size range from 1.5 to 15 mu m. Experimentally determined deposition efficiencies on single spheres are in very good agreement with theoretically predicted results based on a potential flow field as well as a numerical flow simulation. Results in various types of arrays consisting of up to 12 equal-sized spheres show substantial variation of deposition efficiency from sphere to sphere which are strongly influenced by Stokes number and geometry.