The main purposes of this study are to investigate the distributional characteristics of polycyclic aromatic hydrocarbons (PAH) in the vapor and particulate phases in the ambient atmosphere, and to evaluate the effect of ambient temperature on the vapor-particle partitioning during the sampling period. A total of 64 samples were collected during a period of 1995 to 1996, using a medium-volume sampler with XAD-2 adsorbents and quartz fiber filters. Analyses of PAH were carried out using HPLC with UV and Fluorescence detections. In this study, a significant seasonal variation in the distributions was observed, reflecting the effect of ambient temperature on the vapor-particle partitioning of PAH. The relationship between the vapor-particle distributions of the 3 to 5 rings PAH and ambient temperature is considered to be well described using the Langmuir adsorption concept. The estimated empirical constants for each PAH in the relationship, particularly for the more volatile compounds, were also comparable with results from other studies. However, it is still difficult to accurately estimate the initial vapor-particle distribution of PAH in the ambient air, since it is not known to what extent the trapped vapours originated from the particles laden in the filter by being volatilized or from the air samples initially present in the vapour phase. The distribution factors for volatile PAH with 3 to 4 rings appeared to be comparable with those in the literature. It should be noted, however, that these distribution factors give information only about the distribution of PAH between the two phases under a specific sampling condition, and hence may provide only semi -quantitative information on the vapor-particle distributions in the atmosphere.