First established in 1999, the Asian Aerosol Conferences (AACs) have grown rapidly in terms of international participation and the range of topics being discussed, and these now cover virtually every aspect of aerosol science and technology and air quality research. Most selected papers in this special issue were presented at the 7th Asian Aerosol Conference (AAC-2011), which was held in Xi’an, China, from August 17 to 20, 2011. The conference was organized by the Asian Aerosol Research Assembly (AARA), Chinese Association of Aerosol Science and Technology (CAAST), and Institute of Earth Environment, Chinese Academy of Sciences. A total of 550 participants from 21 countries and representing academia, industry, and regulatory agencies attended AAC-2011, which included ~350 plenary, platform, and poster presentations. Some articles were also included in the special issue, even though they were not presented at AAC-2011, due that to their significant contributions to the scientific community.