Initiated in 2007, the Seven South East Asian Studies (7SEAS) seeks to perform interdisciplinary research in the field of aerosol-meteorology and climate interaction in the Southeast Asian region, particularly for the impact of biomass burning on cloud, atmospheric radiation, hydrological cycle, and regional climate. Participating countries include Indonesia, Malaysia, Philippines, Singapore, Thailand, Taiwan, Vietnam, and USA (NASA, NRL, and NOAA). Two pre-studies, Dongsha Experiment and Son La Campaign, were conducted in 2010 and 2011, respectively. Dongsha Experiment was conducted in the northern SE Asian region during March-May. The main goals are (1) to develop the Dongsha Island (about 2 km2, 20°42'52" N, 116°43'51" E) in the South China Sea as an atmospheric observing platform of atmospheric chemistry, radiation and meteorological parameters, and (2) to characterize the chemical and physical properties of biomass burning aerosols in the northern SE Asian region. A monitoring network for ground-based measurements includes the Lulin Atmospheric Background Station (LABS, 2,862 m MSL) in central Taiwan, Hen-Chun (coastal) in the very southern tip of Taiwan, Dongsha Island in South China Sea, Da Nang (near coastal region) in central Vietnam, and Chiang Mai (about 1,400 m MSL) in northern Thailand. Besides, the Mobile Air Quality Station of Taiwan EPA and NASA/COMMIT were shipped to Dongsha Island for continuous measurements of CO, SO2, NOx, O3, and PM10, and aerosol optical and vertical profiles. Two Intensive Observation Periods (IOPs) for aerosol chemistry were conducted during 14-30 March and 10-20 April 2010, respectively. Ten aerosol samplers were deployed for each station for characterizing the compositions of PM2.5/PM10 (some for TSP) including water-soluble ions, metal elements, BC/OC, Hg and dioxins. Sampling tubes of VOCs were also deployed. Concurrent measurements with IOP-1, Taiwanese R/V also made a mission to South China Sea during 14-19 March. Enhanced sounding at Dongsha Island was launched four times per day during the IOPs. This experiment provides a relatively complete dataset of aerosol chemistry and physical observations conducted in the source/sink region for below marine boundary layer and lower free troposphere of biomass burning/air pollutants in the northern SE Asia. Furthermore, the Son La Campaign was conducted in Son La meteorological station (21.33 °N, 103.9 °E; 675m MSL) in northern Vietnam during 18 March – 6 April, 2011. Meanwhile, LABS also conducted a supplementary IOP during 18-30 March. The main goal of this campaign is to characterize the chemical and physical properties of biomass burning aerosols in northern Vietnam. Aerosol sampling was similar to 2010 Dongsha Experiment. Continuous BC measurements were performed. Aerosol optical depth (AOD) was also measured. A depolarized lidar was particularly deployed at Son La for profiling vertical aerosol distributions which were compared with CALIPSO profiles. This presentation will give an overview of these two experiments and their results, particularly for the characterization of biomass burning aerosol at source regions in northern Thailand and northern Vietnam, and receptor station in Taiwan, which is rarely studied.