An investigation at Cape Hedo, Japan, from 2005 to 2006, focused on the long-range transport of organic aerosol(OA) from the Asian continent. An Aerodyne aerosol mass spectrometer was used to investigate the OA data collected over the study. OA concentrations were low from July to September and peaked during March and April. Based on air mass origins, four OA source regions were identified: northern China,southern China, Japan, and Korea. OA concentrations measured at Cape Hedo from the four sources did not exhibit large differences. Conversely, the frequencies of the air masses reaching Cape Hedo from the different regions varied considerably. Northern China was identified as the primary source of organic aerosols at Cape Hedo. Examination of variations in the ratio of m/z44 to OA concentrations with transport time showed that OAs were partially oxidized during transport An investigation at Cape Hedo, Japan, from 2005 to 2006, focused on the long-range transport of organic aerosol (OA) from the Asian continent. An Aerodyne aerosol mass spectrometer was used to investigate the OA data collected over the study. were low from July to September and peaked during March and April. Based on air mass origins, four OA source regions were identified: northern China, southern China, Japan, and Korea. OA concentrations measured at Cape Hedo from the four sources did not exhibit large differences. The frequency of the air masses reaching Cape Hedo from the different regions varied considerably.. Northern China was identified as the primary source of organic aerosols at Cape Hedo. Examination of variations in the ratio of m / z44 to OA concentrations with transport time showed that OAs were partially oxidized during transport