Ten polycyclic aromatic hydrocarbons associated with suspended particulate matter in the ambient air were collected at two sampling sites: urban and suburban residential areas of Yokohama, Japan from 1999 to 2005. The concentrations of target compounds were determined using gas chromatography-mass spectrometry. The total concentrations were higher in urban residential area than suburban residential area. They ranged from 0.31 to 6.16 ng/m3 with a mean of 2.07 ng/m3 and 0.33 to 2.87 ng/m3 with a mean of 1.02 ng/m3 in the urban and suburban residential areas, respectively. The predominant compounds determined both in the urban and suburban residential areas were benzo [b] fluoranthene, benzo [ghi] perylene, indeno [1, 2, 3-cd] pyrene and benzo [e] pyrene. The concentrations of 5- and 6-ring polycyclic aromatic hydrocarbons were higher in the urban than the suburban residential area, accounting for 77.3 % and 72.1% of total polycyclic aromatic hydrocarbons, respectively. Source identification was performed by principal component analysis. Two principal components were identified for each study area and these accounted for 95.9% and 83.3% of total variance, respectively. The results revealed that stationary source and vehicle emissions were the major pollution sources in the studied areas. The impact of emission regulations for automobiles in large Japanese cities, which were enacted during 2002 and 2003, was also studied. Based on the average total concentration, emission reduction was 47.8% and 18.6% in urban residential and suburban residential areas, respectively.