In this study, we attempted to characterize environmental nanoparticles and particle diameter distributions in the atmospheric environment neighboring a traffic route by using a scanning mobility particle sizer (SMPS). The composition of the environmental nanoparticles was analyzed using time-of-flight secondary ion mass spectrometry (TOF-SIMS). It was observed that the environmental nanoparticles showed peaks at 20 nm and 100 nm. The secondary ions C+, O+, Si+, and SiH3+ were strongly detected in the environmental nanoparticles with a peak at 20 nm. On the other hand, the secondary ions NH4+, Na+, K+, and Ca+ were detected in the environmental nanoparticles with a peak at 100 nm. Moreover, it was found that the secondary ion spectral patterns of the organic compounds were different for each particle diameter. Hence, we concluded that the combination of the SMPS with TOF-SIMS is a powerful technique to characterize environmental nanoparticles. (C) 2008 Elsevier B.V. All rights reserved.