To measure the actual exposure of a person to 1-nitropyrene (1-NP) in airborne particulate matter, it is considered more accurate to collect air samples with a portable air sampler than to sample at a fixed location. However, because the portable samplers can sample only small volumes, a sensitive method is needed to analyze the compounds that are collected on a filter. Here we describe a high-performance liquid chromatographic (HPLC) method with fluorescence detection that is sensitive and precise enough for use with portable air samplers. The developed column-switching system successfully removed the interfering substances in the samples with only a simple pretreatment. To improve the precision of the measurement, deuterated 1-NP was used as an internal standard, and it eluted immediately prior to 1-NP with sufficient resolution (R(s), 1.50). The detection limit was 0.32 fmol/injection, and the calibration range was from 2 to 100 fmol. The proposed method was applied to determining 1-NP in fine airborne particulate matter (PM(2.5)) at two sites with low pollution levels. 1-NP was detected in all samples at concentrations in the low fmol/m(3) range. The proposed method has enough sensitivity and precision to determine 1-NP in the limited air volume of the portable sampler.