In the winter and spring of 2002, airborne and ground-based measurements of O3, aerosols, and their precursors were made in the eastern and western North Pacific regions. Three field studies were conducted by an international team of scientists collaborating as part of the Intercontinental Transport and Chemical Transformation (ITCT) program, an activity of the International Global Atmospheric Chemistry (IGAC) project of the International Geosphere-Biosphere Program (IGBP). Previous measurements have indicated that the transport of Asian emissions across the North Pacific Ocean influences the concentrations of trace tropospheric species over the Pacific and even the west coast of North America. In this special section, the recently acquired data are used to better characterize the contribution of continental sources to the aerosol, ozone, and related trace species concentrations over the North Pacific. This overview is aimed at providing the operational and logistical context of the study and introducing the principal findings and conclusions that have been drawn from the results.