We analyzed diesel exhaust particles immediately by fragmentation-free mass spectrometry using ion attachment mass spectrometry (IA-MS). IA-MS can be used to measure labile organic compounds without any fragmentation. Ionization without fragmentation can be performed because a neutral molecule becomes an adduct ion by the attachment of Li(+) with a small amount of energy by the Coulomb force. A third-body gas, such as 100 Pa N(2), removes any excess energy of the adduct ion and makes it stable. The aim is to be able to measure the preprocessing of the sample promptly using this analysis. In a direct analysis of diesel exhaust particles using IA-MS, many compounds (including some unknown chemicals) were detected. In the mass spectrum consisting of the ion peaks of many compounds, it is possible that the source and load factor to the environment are considered as one index.