An aerosol observation campaign was conducted at the summit of Mt. Fuji (at an altitude of 3776m), which is located 170km northwest of Miyakejima. Individual aerosol particles were collected with an electrostatic aerosol sampler and the number–size distribution and composition were examined by electron microscopy. Number–size distributions were measured with the combination of a diffusion battery (DB) and a condensation particle counter. Sulfate and sulfur dioxide concentrations were also determined. During the first half of the campaign (13–15 September 2000), high number fractions of sulfuric-acid containing particles with a mode radius around 0.06μm were observed in the radius range of 0.02–0.2μm coincident with a humid maritime air mass originated from the south. Sulfate and sulfur dioxide also showed high concentrations in this period. These results suggested that the volcanic plumes of Miyakejima were transported up to the summit of Mt. Fuji. Number–size distributions determined by electron microscope were consistent with those derived using the DB. During the later half of the experiment (18–20 September), low fractions of sulfuric-acid containing particles represented only a small fraction of the total particle number, coincident with a dry continental air mass originating from the west.