Measurements of peroxycarboxylic nitric anhydrides (PANs), peroxyacetic nitric anhydride (CH3C(O)OONO2; PAN), and peroxypropionic nitric anhydride (CH3CH2C(O)OONO2; PPN) were made in the spring of 2002, off the west coast of North America, as part of the Intercontinental Transport and Chemical Transformation 2002 (ITCT 2K2) project. Long-range transport of Asian emissions was observed in which PAN and PPN mixing ratios were as high as 650 pptv and 90 pptv, respectively. Moreover, these two species constituted as much as 80% of the odd nitrogen (NOy) in those air masses, and median PAN/NOy was more than 60% at altitudes of 4 km and above. Systematic differences in the ratio of PPN to PAN were observed in air masses that had been impacted by Asian urban emissions relative to those impacted by biomass burning. Mixing ratios of PAN and PPN were also elevated in the marine boundary layer close to the west coast of California, possibly because of photochemical production driven by maritime NOx emissions.