Morphological changes of agglomerates consisting of nanometer primary gold particles were studied experimentally and theoretically. Gold aerosol nanoparticles were produced using the evaporation/condensation method, and the change in agglomerate size by reheating was examined experimentally using a tandem DMA setup. Numerical calculations, based on two extreme mechanisms to reshape agglomerates, i.e., subsequent coalescence of primary particles and subsequent rearrangement of primary particles, were carried out. By comparison with the experimental results, the sintering time and the rate constant of restructuring were obtained. Using these values, the change in particle size for different generation conditions could be calculated. The change in morphology of agglomerates can be explained from the comparison of the experimental results with the theoretical calculations: agglomerates with smaller primary particles will compact mainly by the subsequent coalescence of primary particles, while agglomerates with larger primary particles will compact mainly by a rearrangement of primary particles. (C) 2002 Elsevier Science Ltd. All rights reserved.