We developed the measurement method for the complex particulate matter in urban air environment using micro-beam analyses [electron probe microanalysis (EPMA), field emission type scanning electron microscope (FE-SEM), and TOF-SIMS]. In this study, the environmental particles collected at the location near both the traffic route and the railroad were characterized. By the EPMA analysis and FE-SEM observation, it became clear that many iron particles adsorbed smaller environmental particles on surface. The most of adsorbed particles were the carbonaceous particles containing small amount of silicon, as observed from the results of TOF-SIMS measurement. From these results, we concluded that the complex particles such as the iron particles emitted from a railroad combined with diesel exhaust particles (DEPs) were suspended in the urban air environment. (C) 2004 Elsevier B.V. All rights reserved.