The temporal trend of the particulate polycyclic aromatic hydrocarbon (PAH) level was observed at Gosan, a background site in Korea, for 4 years between November 2001 and January 2004. The total average concentration of ambient particulate PAH compounds was 3.65 ¿ 4.74 ng m-3, which was mainly affected by a rather small number of very high PAH level samples. The PAH level at Gosan was 1 or 2 orders higher than those at other remote sites and 1 or 2 orders lower than those in urban areas in northeast Asia. The particulate PAH concentrations were high during cold periods mainly because of the seasonal variation of fossil fuel usage amount in northeast Asia. When the PAH levels were high, the ratio of BeP-to-BaP was also high, which is an indicator of particle residence time in the air. On the basis of the backward trajectory and upper wind direction analyses, it was observed that when air parcels were from China, the PAH levels were high. Also, the compositions of PAH compound ratios were similar to those in Beijing in winter. These indicate influence of emissions from China, especially from coal combustion and long-range transport. The relationship between the concentrations of PAHs and non-sea-salt-(nss)-SO42- was generally good when the PAH levels were high. However, the periods of peaks were different, implying different emission patterns.